JP7141607B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet. More specifically, the present invention relates to a removable pressure-sensitive adhesive sheet.

Removable pressure-sensitive adhesive sheets are used in various applications such as distribution management labels and office supplies.
Removable pressure-sensitive adhesive sheets are usually required to have both adhesiveness and releasability, which are contradictory properties. For example, it is required to exhibit sufficient adhesiveness even on rough surfaces such as corrugated cardboard when used, but not to be easily peeled off. When the removable pressure-sensitive adhesive sheet is peeled off from the adherend, it is required to be able to peel cleanly without leaving adhesive residue on the adherend or damaging the adherend. In addition, there is also a demand for a performance that allows repeated application and detachment to and from an adherend.

Removable pressure-sensitive adhesive sheets include those having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a spherical pressure-sensitive adhesive. By using such a pressure-sensitive adhesive layer, it is possible to achieve both appropriate adhesiveness to an adherend and releasability.
For example, Patent Document 1 discloses a removable pressure-sensitive adhesive sheet using an adhesive elastomeric copolymer as a spherical pressure-sensitive adhesive, in which part of the spherical pressure-sensitive adhesive is exposed from the surface of the pressure-sensitive adhesive layer. As a result, the contact area when the pressure-sensitive adhesive layer and the adherend are brought into contact with each other is suppressed, and the adhesion, peelability, and re-adhesion properties of the pressure-sensitive adhesive sheet are compatible.

JP-A-50-2736

By the way, when a removable adhesive sheet is distributed as a product, a release material having a release agent layer provided on a release material substrate is laminated on the adhesive layer in order to protect the adhesive layer. be. Conventionally, in a removable pressure-sensitive adhesive sheet, the release agent layer of the release material is generally formed from a silicone-based release agent composition.
However, the release agent layer formed from the silicone-based release agent composition is excellent in releasability, and therefore, it is difficult to maintain the lamination state when the pressure-sensitive adhesive layer in contact with the release agent layer has low adhesive strength. rice field. For example, when the adhesive sheet is rewound for some processing, just by passing the adhesive sheet through the guide rolls, the release material rises straight from the adhesive layer in parallel to the axial direction of the guide rolls, a so-called tunneling phenomenon. has happened. In particular, when a spherical adhesive is used in the adhesive composition, since the adhesive layer and the release agent layer are held in point contact, such a tunneling phenomenon occurs remarkably. When the pressure-sensitive adhesive sheet undergoes tunneling, problems arise such that the pressure-sensitive adhesive sheet cannot be processed, and dust adheres to the surface of the pressure-sensitive adhesive layer, making it impossible to obtain desired adhesive physical properties.

In addition, when the release agent layer of the release material is formed of a silicone-based release agent composition, the release agent layer laminated surface of the release material base material is separated from the release agent layer laminated surface of the release material substrate in the process of winding the release material into a roll during the manufacturing process. The surface on the opposite side (hereinafter also referred to as "the surface of the release material substrate") contacts the release agent layer, and the silicone compound derived from the silicone-based release agent composition may adhere to the surface of the release agent substrate. be.
Then, in the process of laminating the release material on the adhesive layer and winding the laminate into a roll, the silicone compound adhering to the surface of the base material for the release material becomes the base material for the pressure-sensitive adhesive sheet that supports the pressure-sensitive adhesive layer. may adhere to the surface opposite to the surface on which the adhesive layer is laminated (hereinafter also referred to as "surface of base material for adhesive sheet").
The surface of the pressure-sensitive adhesive sheet substrate can be used as a printing/printing surface or a writing surface. Therefore, if a silicone compound adheres to the surface of the pressure-sensitive adhesive sheet base material, the ink tends to be repelled, resulting in printing/printing defects and writing defects.

An object of the present invention is to provide a pressure-sensitive adhesive sheet capable of suppressing the adhesion of a silicone compound to the surface of a pressure-sensitive adhesive sheet substrate while suppressing the occurrence of a tunneling phenomenon at the interface between a release agent layer and a pressure-sensitive adhesive layer. and

As a result of intensive investigations by the present inventors, the release agent layer contains a non-silicone thermoplastic resin as a main component and is formed from a release agent composition containing a silylated polyolefin. We have found that the above problems can be solved.

That is, the present invention relates to the following [1] to [4].
[1] A pressure-sensitive adhesive sheet having a laminated structure in which a pressure-sensitive adhesive sheet substrate, a pressure-sensitive adhesive layer, a release agent layer, and a release agent substrate are laminated in this order, wherein the release agent layer is a non-silicone type A pressure-sensitive adhesive composition comprising a thermoplastic resin (A) as a main component and a layer formed from a release agent composition containing a silylated polyolefin (B), wherein the pressure-sensitive adhesive layer contains a spherical pressure-sensitive adhesive (C). An adhesive sheet, which is a layer formed from
[2] The adhesive sheet according to [1] above, wherein the non-silicone thermoplastic resin (A) is an olefin resin (A1) other than the silylated polyolefin (B).
[3] The above [1], wherein the mass ratio (B/A) of the content of the silylated polyolefin (B) to the content of the non-silicone thermoplastic resin (A) is 1/99 to 30/70. Or the pressure-sensitive adhesive sheet according to [2].
[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the peel force when peeling the release agent layer from the pressure-sensitive adhesive layer is 200 to 800 mN/25 mm.

According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet capable of suppressing the adhesion of a silicone compound to the surface of a pressure-sensitive adhesive sheet base material while suppressing the occurrence of a tunneling phenomenon at the interface between the release agent layer and the pressure-sensitive adhesive layer. becomes possible.

1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet of one embodiment of the present invention; FIG.

As used herein, the term “active ingredient” refers to the components contained in the composition, excluding the diluent solvent.
In addition, in the present invention, the lower limit and upper limit values described stepwise for preferred numerical ranges (for example, ranges of content etc.) can be independently combined. For example, from the statement "preferably 10 to 90, more preferably 30 to 60", combining "preferred lower limit (10)" and "more preferred upper limit (60)" to "10 to 60" can also

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a laminated structure in which a pressure-sensitive adhesive sheet substrate, a pressure-sensitive adhesive layer, a release agent layer, and a release agent substrate are laminated in this order, wherein the release agent layer comprises: A layer formed from a release agent composition containing a non-silicone thermoplastic resin (A) as a main ingredient and containing a silylated polyolefin (B), wherein the pressure-sensitive adhesive layer contains a spherical pressure-sensitive adhesive (C). The pressure-sensitive adhesive sheet is a layer formed from the pressure-sensitive adhesive composition.
Hereinafter, after explaining the configuration of the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive sheet base material, the pressure-sensitive adhesive layer, the release agent layer, and the release material base material, which constitute the pressure-sensitive adhesive sheet of the present invention, will be described. After that, the properties, manufacturing method, and uses of the pressure-sensitive adhesive sheet of the present invention will be further described.

[Structure of Adhesive Sheet]
The pressure-sensitive adhesive sheet of the present invention has a laminated structure in which a pressure-sensitive adhesive sheet base material, an adhesive layer, a release agent layer, and a release material base material are laminated in this order.
FIG. 1 is a schematic cross-sectional view showing a pressure-sensitive adhesive sheet of one embodiment of the present invention. The adhesive sheet 1 has a laminated structure in which an adhesive sheet substrate 11, an adhesive layer 12, a release agent layer 13, and a release material substrate 14 are laminated in this order. In other words, the pressure-sensitive adhesive sheet 1 is composed of a pressure-sensitive adhesive sheet substrate 11, a pressure-sensitive adhesive layer 12, and a release material 15 having a release agent layer 13 and a release agent substrate 14, which are laminated in this order. It has a laminate structure in which the adhesive layer 13 side is in direct contact with the adhesive layer 12 .
The pressure-sensitive adhesive sheet 1 shown in FIG. Laminated directly without intermediary. That is, the pressure-sensitive adhesive sheet 1 shown in FIG. 1 is a pressure-sensitive adhesive sheet consisting only of the pressure-sensitive adhesive sheet substrate 11, the pressure-sensitive adhesive layer 12, the release agent layer 13, and the release material substrate 14. FIG. However, the pressure-sensitive adhesive sheet of the present invention is not limited to such embodiments, and between the pressure-sensitive adhesive sheet substrate 11 and the pressure-sensitive adhesive layer 12, between the pressure-sensitive adhesive layer 12 and the release agent layer 13, and between the release agent layer 13 Another layer may be provided between at least one of the agent layer 13 and the release material base material 14 . Further, another layer may be provided on at least one of the surface of the adhesive sheet base material 11 and the surface of the release material base material 14 .

[Base material for adhesive sheet]
The pressure-sensitive adhesive sheet base material of the pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it functions at least as a support for the pressure-sensitive adhesive layer. are appropriately selected according to the purpose of use of the adhesive sheet.
Examples of such adhesive sheet substrates include papers such as kraft paper, fine paper, glassine paper, parchment paper, rayon paper, coated paper, and synthetic fiber paper; polyester resins, polyvinyl chloride resins, Resin films such as polyvinylidene chloride-based resins and polyolefin-based resins; synthetic paper;
The pressure-sensitive adhesive sheet base material may be a single layer, or may be a multilayer of two or more layers of the same or different types.
Further, a coat layer may be provided on the surface of the adhesive sheet base material. Examples of the coat layer include a print-receiving layer in consideration of printing suitability for various displays, but it is not necessarily limited to the print-receiving layer, and it is possible to improve abrasion resistance, storage stability, waterproofness, designability, and the like. Various coating layers considered may be provided.
The coat layer may be a single layer, or may be multiple layers of two or more layers of the same or different types.

The thickness of the pressure-sensitive adhesive sheet substrate is appropriately selected depending on the purpose of use of the pressure-sensitive adhesive sheet, and from the viewpoint of handleability, the thickness is preferably 10 to 200 μm, more preferably 20 to 150 μm, and still more preferably 30 to 100 μm. is.

Further, when a synthetic resin is used as the adhesive sheet base material, the surface of the adhesive sheet base material that is in contact with the adhesive layer may be provided with: If desired, the surface can be treated by a method such as an oxidation method or a roughening method.
Examples of the oxidation method include corona discharge surface treatment, chromic acid surface treatment (wet), flame surface treatment, hot air surface treatment, ozone/ultraviolet irradiation surface treatment, and the like. In addition, examples of the roughening method include a sandblasting method, a solvent treatment method, and the like. These surface treatment methods are appropriately selected according to the type of adhesive sheet base material, but in general, the corona discharge surface treatment method is preferably used from the viewpoint of effects and operability. A primer treatment can also be applied.
In addition, when providing a coat layer on the surface of the base material for adhesive sheets, you may perform these surface treatments with respect to the base material surface for adhesive sheets.

[Adhesive layer]
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is formed from a pressure-sensitive adhesive composition containing a spherical pressure-sensitive adhesive (C).
In the removable pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer has a relatively high adhesive strength when lightly pressed to adhere to an adherend, and the adhesive strength does not increase significantly even when strongly pressed to adhere to the adherend. A performance that can be peeled off with a relatively small force is desired. In addition, it is also desired to prevent the adhesive layer from being partially transferred to the surface of the adherend when peeled off, leaving an adhesive residue or damaging the adherend. Furthermore, it is desired to have the ability to adhere to another adherend again with good adhesiveness after peeling.
From this point of view, in the present invention, a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing the spherical pressure-sensitive adhesive (C) is used. In such an adhesive layer, a part of the adhesive fine spherical particles derived from the spherical adhesive (C) contained in the adhesive composition is exposed on the surface of the adhesive layer. Therefore, when the adherend is brought into contact with the pressure-sensitive adhesive layer, the contact area between the adherend and the pressure-sensitive adhesive layer is reduced. Therefore, the pressure-sensitive adhesive layer has both appropriate adhesiveness and releasability from the adherend, and the above performance can be ensured.

Note that the pressure-sensitive adhesive composition of one embodiment of the present invention may contain additives for pressure-sensitive adhesives, if necessary.
Each component contained in the pressure-sensitive adhesive composition, which is the material for forming the pressure-sensitive adhesive layer, will be described below.

<Spherical adhesive (C)>
The adhesive composition contains a spherical adhesive (C).
The spherical pressure-sensitive adhesive (C) is not particularly limited as long as it is a pressure-sensitive adhesive composed of fine spherical particles. can be used.
Specific examples of the spherical pressure-sensitive adhesive (C) include acrylic spherical pressure-sensitive adhesives and rubber-based spherical pressure-sensitive adhesives.
The spherical adhesive (C) may be used alone or in combination of two or more.
Among these, it is preferable to use the acrylic spherical pressure-sensitive adhesive (C1) from the viewpoint of facilitating control of appropriate adhesiveness and releasability to the adherend.

Acrylic spherical pressure-sensitive adhesive (C1) is a spherical pressure-sensitive adhesive made of an acrylic polymer. The acrylic polymer includes an acrylic homopolymer obtained by polymerizing one type of acrylic monomer, an acrylic copolymer obtained by polymerizing two or more types of acrylic monomers, and and acrylic copolymers obtained by polymerizing acrylic monomers and monomers other than acrylic monomers.
In the acrylic spherical pressure-sensitive adhesive (C1), the acrylic polymer and acrylic copolymer may be used singly or in combination of two or more.

Specific examples of acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, ) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, etc. (meth)acrylic acid esters having 1 to 20 alkyl groups; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate Hydroxyalkyl (meth)acrylates such as acrylates, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N-methylmethacrylamide , N,N-dimethyl methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, and other acrylamides; Alkyl; (meth)acrylic acid and the like.
In this specification, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid", and the same applies to other similar terms.

Specific examples of monomers other than acrylic monomers include ethylenically unsaturated carboxylic acids such as crotonic acid, maleic acid, itaconic acid and citraconic acid; vinyl esters such as vinyl acetate and vinyl propionate; olefins such as propylene and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene monomers such as styrene and α-methylstyrene; diene monomers such as butadiene, isoprene and chloroprene; Examples thereof include nitrile-based monomers such as lonitrile.

Here, the polymer constituting the acrylic spherical pressure-sensitive adhesive (C1) may be crosslinked with an internal crosslinking agent or an external crosslinking agent.
An internal cross-linking agent is a reactive monomer capable of introducing a cross-linked structure into a polymer molecule during polymerization.
An external cross-linking agent refers to a compound capable of reacting with a cross-linkable functional group present in a polymer molecule to introduce a cross-linked structure.

Specific examples of the internal cross-linking agent include polyfunctional ethylenically unsaturated monomers, keto group-containing ethylenically unsaturated monomers, and the like.
The internal cross-linking agents may be used singly or in combination of two or more.
When using an internal cross-linking agent, the internal cross-linking agent is incorporated into the monomer mixture. The content of the internal cross-linking agent is preferably 5 parts by mass or less with respect to 100 parts by mass of the monomer component.

Specific examples of external cross-linking agents include isocyanate compounds, epoxy compounds, melamine compounds, aziridine (ethyleneimine) compounds, hydrazide compounds, oxazoline compounds, carbodiimide compounds, urea compounds, dialdehyde compounds, Metal chelate compounds, metal alkoxides, metal salts and the like are included.
The external cross-linking agents may be used singly or in combination of two or more.
When using an external cross-linking agent, the external cross-linking agent is incorporated into the resulting polymerization reaction solution or dispersion. The amount of the external cross-linking agent to be blended is preferably 5 parts by mass or less per 100 parts by mass of the polymer.

The acrylic spherical pressure-sensitive adhesive can be obtained as an aqueous suspension of a spherical pressure-sensitive adhesive by a conventionally known method such as a suspension polymerization method or a method of suspending in water after solution polymerization.

The average particle diameter of the particles of the spherical adhesive (C) to be blended in the adhesive composition is usually 1-200 μm, preferably 10-100 μm, more preferably 15-50 μm. When the average particle diameter of the particles of the spherical adhesive (C) blended in the adhesive composition is within the above range, the adhesive strength when the adhesive layer is lightly pressed against the adherend to be adhered can be relatively high. Even when it is pressed and adhered strongly, the adhesive force does not increase so much and the adhesive can be easily peeled off with a relatively small force. In addition, it is easy to prevent a part of the pressure-sensitive adhesive layer from being transferred to the surface of the adherend when the adhesive layer is peeled off, resulting in an adhesive residue or damage to the adherend. In addition, it is easy to adhere to another adherend again with good adhesion after peeling.

The average particle size of the particles of the spherical adhesive (C) blended in the adhesive composition is calculated by, for example, randomly selecting about 100 particles from an electron micrograph, measuring their particle sizes, and calculating the average value. can be obtained by doing If the particle is not a true sphere, the major axis and minor axis are determined, and the average value thereof may be assumed to be the particle diameter of the particle.

<Binder Adhesive>
The adhesive composition contains a binder adhesive together with the spherical adhesive (C).
The binder adhesive is not particularly limited as long as it is an adhesive capable of fixing the spherical adhesive (C) to the adhesive sheet substrate.
Specific examples of binder adhesives include adhesives whose main component is an emulsion containing a (meth)acrylic acid ester polymer (hereinafter also referred to as "acrylic emulsion-type adhesive").
Here, the "main component" means a component having the largest content (mass ratio) in the binder adhesive, preferably 50% by mass or more based on the total amount (100% by mass) of the binder adhesive, preferably It means a component that accounts for 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and even more preferably 90% by mass or more.

As the (meth)acrylic ester-based polymer, any one can be appropriately selected and used from (meth)acrylic ester-based polymers used in ordinary acrylic pressure-sensitive adhesives.
Specific examples of such (meth)acrylic ester polymers include homopolymers or copolymers obtained by polymerizing one or more acrylic ester monomers, or acrylic ester monomers. and a copolymer obtained by polymerizing a monomer other than an acrylic acid ester-based monomer.
Specific examples of the monomer used for producing the (meth)acrylic acid ester polymer include those shown in the acrylic spherical pressure-sensitive adhesive (C1).

The (meth)acrylate polymer may be crosslinked with an internal crosslinking agent or an external crosslinking agent.
Specific examples of the internal cross-linking agent and the external cross-linking agent include those exemplified in the description of the spherical pressure-sensitive adhesive (C).

An acrylic emulsion-type adhesive can be produced by a known method.
For example, an acrylic emulsion-type pressure-sensitive adhesive can be produced by adding a predetermined monomer to an aqueous medium containing an emulsifier, performing emulsification, and performing emulsion polymerization in the presence of a polymerization initiator.
The average particle size of the micelles in the acrylic emulsion pressure-sensitive adhesive is not particularly limited. The average particle size range is usually 100-2000 nm, preferably 120-1500 nm, particularly preferably 150-500 nm.

<Other additives>
In one aspect of the present invention, the pressure-sensitive adhesive composition may optionally contain additives for pressure-sensitive adhesives.
Examples of adhesive additives include tackifiers, plasticizers, fillers, antioxidants, ultraviolet absorbers, preservatives, antifungal agents, dyes, pigments, fragrances, and the like.
The content of these additives is usually 10 parts by mass or less, preferably 1 to 5 parts by mass, based on the total amount (100 parts by mass) of the adhesive composition.

<Content and content ratio of each component in the adhesive composition>
In one aspect of the present invention, the mass ratio of the active ingredients of the spherical pressure-sensitive adhesive (C) and the acrylic emulsion-type pressure-sensitive adhesive contained in the pressure-sensitive adhesive composition (spherical pressure-sensitive adhesive (C): acrylic emulsion-type pressure-sensitive adhesive) is It is preferably 100:75 to 100:250, more preferably 100:80 to 100:220.
By setting the mass ratio of the active ingredient of the spherical pressure-sensitive adhesive (C) and the acrylic emulsion-type pressure-sensitive adhesive contained in the pressure-sensitive adhesive composition to the above range, the adhesion between the pressure-sensitive adhesive sheet substrate and the pressure-sensitive adhesive layer can be improved. Easy to assume. In addition, it is easy to improve the re-adherability to the adherend.

<Dilution solvent>
The adhesive composition is diluted with water, for example, and used in the form of an aqueous solution.
Specifically, an aqueous solution of the pressure-sensitive adhesive composition can be obtained by mixing an aqueous suspension of the spherical pressure-sensitive adhesive (C), an acrylic emulsion-type pressure-sensitive adhesive, the above additives, and the like.
The amount of water may be appropriately selected so that the pressure-sensitive adhesive composition has an appropriate viscosity when applied.

[Release agent layer]
The release agent layer of the pressure-sensitive adhesive sheet of the present invention may be a layer formed from a release agent composition containing a non-silicone thermoplastic resin (A) as a main agent and containing a silylated polyolefin (B). The release agent composition may contain a release agent additive, if necessary.
In one aspect of the present invention, the total content of the components (A) and (B) in the release agent composition is preferably 70% by mass or more based on the total amount (100% by mass) of the release agent composition, More preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more.
Each component contained in the release agent composition, which is the material for forming the release agent layer, will be described below.

<Non-Silicone Thermoplastic Resin (A)>
The release agent composition contains a non-silicone thermoplastic resin (A) as a main ingredient.
In this specification, the "main agent" means a component having the largest content (mass ratio) in the release agent composition, preferably 50% based on the total amount (100% by mass) of the release agent composition. It means a component occupying more than mass %.
In one aspect of the present invention, from the viewpoint of facilitating control of the release force of the release agent layer to an appropriate value, the content of the non-silicone thermoplastic resin (A) in the release agent composition is Based on the total amount (100% by mass) of, preferably 50 to 99% by mass, more preferably 60 to 97% by mass, still more preferably 65 to 95% by mass.

The non-silicone thermoplastic resin (A) is not particularly limited as long as it is a thermoplastic resin that does not substantially contain a silicone compound.
In the present specification, the term "thermoplastic resin substantially free of silicone compounds" means to exclude thermoplastic resins intentionally blended with silicone compounds for a specific reason. . Specifically, the content of the silicone compound is preferably less than 1.0% by mass, more preferably less than 0.1% by mass, and still more preferably 0.01% by mass, based on the total amount (100% by mass) of the release agent layer. It means less than % by mass.

Specific examples of the non-silicone thermoplastic resin (A) include olefin resin; polyvinyl chloride; polyvinylidene chloride; ethylene vinyl acetate copolymer; ethylene/methyl methacrylate copolymer; polyester such as polyethylene terephthalate; polycarbonate; polyamide; ABS resin; polyacetal resin; polyimide; polyurethane;
The non-silicone thermoplastic resin (A) may be used singly or in combination of two or more.

Here, in one aspect of the present invention, from the viewpoint of facilitating control of the release force of the release agent layer to an appropriate value, the non-silicone thermoplastic resin (A) is preferably an olefin resin (A1). preferable.
The olefinic resin (A1) does not include the silylated polyolefin (B). That is, the olefinic resin (A1) is an olefinic resin other than the silylated polyolefin (B).

The olefin resin (A1) is a polymer mainly composed of structural units (a1) derived from the olefin monomer (a1').
However, it does not include a structural unit (b1) derived from a hydrosilane compound (b1') containing one or more of general formula (1) described later as a structural unit.
Here, "a polymer mainly composed of structural units (a1) derived from an olefin monomer (a1')" means that among the structural units contained in the olefin-based resin (A1), the structural unit contained in the largest amount is an olefin It means that the structural unit (a1) is derived from the monomer (a1').
As the olefin monomer (a1'), an olefin having 2 to 8 carbon atoms is preferred. Examples of olefins having 2 to 8 carbon atoms include ethylene, propylene, butylene, isobutylene, 1-hexene and the like.
In one aspect of the present invention, the olefin monomer (a1′) is more preferably ethylene, propylene, or butylene, which are olefins having 2 to 4 carbon atoms, and ethylene or propylene, which is olefins having 2 to 3 carbon atoms. is more preferred.
One of the olefin monomers (a1') may be used alone, or two or more of them may be used in combination to form a copolymer.

Specific examples of the olefin resin (A1) include ultra-low density polyethylene (VLDPE, density: 880 kg/m3 or more and less than 910 kg/m3) ^, low density polyethylene ⁽ LDPE ^, density: 910 kg/m3 or more and 915 kg/m3). ³ ), medium density polyethylene (MDPE, density: 915 kg/m ³ or more and less than 942 kg/m ³ ), high density polyethylene (HDPE, density: 942 kg/m ³ or more), linear polyethylene, etc. polyethylene resin; polypropylene resin (PP); polybutene resin (PB); ethylene-propylene copolymer; olefin elastomer (TPO); ethylene-vinyl acetate copolymer (EVA); ethylene-methyl methacrylate copolymer (EMMA); ethylene-propylene - Olefin-based terpolymers such as (5-ethylidene-2-norbornene); and the like, preferably polyethylene resin (PE), polypropylene resin (PP), polybutene resin (PB), more preferably They are polyethylene resin (PE) and polypropylene resin (PP).
The olefin resin (A1) may be used alone or in combination of two or more.

The content of the structural unit (a1) in the olefinic resin (A1) is preferably 50 to 100% by mass, more preferably 50 to 100% by mass, based on the total structural units (100% by mass) of the olefinic resin (A1). is 60 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass.

Further, the content of structural units derived from olefins having 2 to 3 carbon atoms in the olefin resin (A1) is preferably 50 to 100 mass with respect to all structural units (100 mass%) of the olefin resin. %, more preferably 60 to 100% by mass, still more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass.

<Silylated polyolefin (B)>
The release agent composition further comprises a silylated polyolefin (B).
If the release agent layer is formed of a release agent composition comprising a non-silicone thermoplastic resin (A), the release force becomes too large, making it difficult to separate the release material from the pressure-sensitive adhesive layer. In addition, when the release agent layer is formed of a release agent composition comprising a silicone-based thermoplastic resin (A) as in the past, the release force is too small, and a tunneling phenomenon occurs at the interface between the release agent layer and the pressure-sensitive adhesive layer. easier. As a result, problems such as poor workability and failure to protect the pressure-sensitive adhesive layer with a release material tend to occur.
In view of these circumstances, the present inventors have proposed using a release agent layer formed from a release agent composition containing a non-silicone thermoplastic resin (A) as a main component and containing a silylated polyolefin (B). It has been found that by appropriately controlling the release force, the occurrence of tunneling phenomenon at the interface between the release agent layer and the pressure-sensitive adhesive layer can be suppressed, and furthermore, the problem of migration of the silicone compound can be solved.

The silylated polyolefin (B) is a structural unit (b1) derived from a hydrosilane compound (b1′) (hereinafter also referred to as “monomer (b1′)”) containing one or more of the following general formula (1) as a structural unit. , and a structural unit (b2) derived from a terminal double bond-containing polyolefin (b2′) (hereinafter also referred to as “monomer (b2′)”).
The silylated polyolefin (B) is obtained by reacting -Si-H in the hydrosilane compound (b1') with -C=C (vinyl group) in the terminal double bond-containing polyolefin (b2'), -Si- Contains a CC-structure.
The polymerization form of the copolymer of the hydrosilane compound (b1′) and the terminal double bond-containing polyolefin (b2′) is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer. However, it is preferably a block copolymer.

In general formula (1) above, R ¹ represents a hydrocarbon group or a silicon-containing group. R ¹ is preferably a hydrocarbon group, more preferably an aliphatic hydrocarbon group, still more preferably an alkyl group, still more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably methyl is the base.
Y ¹ represents an oxygen atom, a sulfur atom or NR (N is a nitrogen atom and R represents a hydrogen atom or a hydrocarbon group). Y ¹ is preferably an oxygen atom.
When there are a plurality of R ¹ and Y ¹ , they may be the same or different, but are preferably the same.
Here, the hydrosilane compound (b1') is preferably a compound represented by the following general formula (2).

In general formula (2) above, R ¹ and Y ¹ represent the same as in general formula (1) above.
R ^1b represents a hydrocarbon group, preferably an aliphatic hydrocarbon group, more preferably an alkyl group, still more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably a methyl group .
^Y2 represents an oxygen atom, a sulfur atom or NR (N is a nitrogen atom and R represents a hydrogen atom or a hydrocarbon group). ^Y2 is preferably an oxygen atom.
m is an integer of 1-20, preferably an integer of 1-6.
n is an integer from 0 to 20, preferably 0 or 1;
When n is 1 or more, Z represents a divalent linking group represented by the following general formula (4).
When n is 0, Z represents a divalent linking group represented by the following general formula (4) or a direct bond between Y ¹ and R ^1c .
R ^1a and R ^1c each represent a hydrocarbon group or a group represented by the following general formula (3). The hydrocarbon group is preferably an aliphatic hydrocarbon group, more preferably an alkyl group, still more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably a methyl group. However, when n is 0, R ^1c may be a hydrogen atom. When a plurality of R ¹ , R ^1a , R ^1b and R ^1c are present, they may be the same or different.
When there are a plurality of Y ¹ and Y ² , they may be the same or different, but they are all preferably oxygen atoms.

In the above general formula (3), R ²¹ represents a hydrocarbon group, preferably an aliphatic hydrocarbon group, more preferably an alkyl group, still more preferably an alkyl group having 1 to 3 carbon atoms, A methyl group is particularly preferred. A plurality of R ²¹ may be the same or different, but they are preferably the same.
y is an integer from 1 to 100, preferably 1;

In the above general formula (4), R ¹¹ represents a hydrocarbon group, preferably an aliphatic hydrocarbon group, more preferably an alkyl group, still more preferably an alkyl group having 1 to 3 carbon atoms, A methyl group is particularly preferred.
A plurality of R ¹¹ may be the same or different, but they are preferably the same.
l is an integer from 0 to 500;

Moreover, the hydrosilane compound (b1') may have a structure represented by the following general formula (5).
In addition, in the following general formula (5), l is the same as in the above general formula (4).

The terminal double bond-containing polyolefin (b2') is a terminal double bond-containing polyolefin containing one or more vinyl groups.
In the terminal double bond-containing polyolefin (b2'), the portion other than the vinyl group of the terminal double bond-containing polyolefin is selected from the group consisting of an ethylene homopolymer chain, a propylene homopolymer chain, or an olefin having 2 to 50 carbon atoms. It is preferably a copolymer chain of two or more olefins.
Among these, ethylene homopolymer chains, propylene homopolymer chains, or consisting of ethylene, propylene, butene, vinylnorbornene, cyclic polyenes having two or more double bonds and linear polyenes having two or more double bonds It is preferably a copolymer chain of two or more olefins selected from the group, particularly an ethylene homopolymer chain, a propylene homopolymer chain, a copolymer chain of an olefin and a diene, a copolymer chain of ethylene and propylene, and an ethylene and norbornene copolymer chains are preferred.
Further, the number average molecular weight of the terminal double bond-containing polyolefin (b2') is preferably 100 to 500,000.
The number average molecular weight (Mn) is a value converted to standard polystyrene measured by gel permeation chromatography (GPC).

The silylated polyolefin (B) is, for example, a hydrosilane compound (b1′) and a terminal double bond-containing polyolefin (b2′), as described in JP-A-2010-37555 and JP-A-2011-26448. in the presence of a transition metal catalyst composition prepared from a hydrosilane compound (b1′) and a transition metal halide.

The amount ratio of the hydrosilane compound (b1′) and the terminal double bond-containing polyolefin (b2′) varies depending on the structure of the silylated polyolefin (B) to be produced, but usually the terminal double bond-containing polyolefin (b2′ ) to the Si—H bond in the hydrosilane compound (b1′) is in the range of 0.01 to 10 equivalents, preferably 0.1 to 2 equivalents.

Specific examples of the silylated polyolefin (B) include olefin-silicone copolymers having a structure having polyorganosiloxane blocks (silicone blocks) represented by the following general formulas (6) to (8). However, the silylated polyolefin (B) is not limited to these.
In general formulas (6) to (8) below, l and m are the same numerical values as l and m described in general formulas (2) and (4) above. The value of l is preferably 5 to 200, more preferably 10 to 100, from the viewpoint of facilitating control of the release force of the release agent layer to an appropriate value.
In addition, p is an integer of 1 or more, preferably 100 to 100,000, more preferably 200 to 10,000.
In general formulas (6) to (8) below, two R ³¹ in terminal double bond-containing polyolefin (b2′) independently represent a hydrogen atom or a hydrocarbon group. ^R31 is the residue of an olefin unit that constitutes polyolefin. When the olefin is ethylene, both R ³¹ are hydrogen atoms. When the olefin is propylene, the two R ³¹ are a combination of hydrogen atoms and methyl groups. When there are multiple p's, the values of p may be the same or different.

In one aspect of the present invention, from the viewpoint of facilitating control of the release force of the release agent layer to an appropriate value, the content of the silylated polyolefin (B) in the release agent composition is the total amount (100 %), preferably 1 to 30% by mass, more preferably 3 to 20% by mass, even more preferably 5 to 20% by mass, and even more preferably 7 to 20% by mass.

<Other additives>
In one aspect of the present invention, the release agent composition may optionally contain release agent additives in addition to the components (A) and (B) described above.
Examples of such additives include antioxidants, ultraviolet absorbers, antistatic agents, surfactants, photoinitiators, light stabilizers, and the like.
The content of these additives is usually 10 parts by mass or less, preferably 1 to 5 parts by mass, based on the total amount (100 parts by mass) of the release agent composition.
Further, in one aspect of the present invention, the release agent composition may be in a form that allows solution coating by adding a diluent solvent to the various active ingredients described above.

<Content and content ratio of each component in the release agent composition>
In one aspect of the present invention, from the viewpoint of easily controlling the release force of the release agent layer to an appropriate value, the mass of the content of the silylated polyolefin (B) with respect to the content of the non-silicone thermoplastic resin (A) The ratio (B/A) is preferably 1/99 to 30/70, more preferably 3/97 to 20/80, even more preferably 5/95 to 20/80, and 7 /93 to 20/80 is even more preferable.

<Thickness of Release Agent Layer>
The thickness of the release agent layer is not particularly limited, but is usually 5 to 70 μm, preferably 5 to 50 μm, more preferably 5 to 40 μm, even more preferably 5 to 30 μm, still more preferably 10 to 20 μm. is.
The thickness of the release agent layer is measured, for example, by the method described in Examples below.

[Base material for release material]
The release liner base material of the pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it functions as a support for supporting the release liner. is appropriately selected from.
Specific examples include the above-described paper substrates, resin films or sheets, substrates obtained by laminating a paper substrate with a resin, and the like, which are used as substrates for pressure-sensitive adhesive sheets.
The base material for a release material may be a single layer, or may be a multilayer consisting of two or more layers of the same or different types.
The thickness of the base material for release material is not particularly limited, but it is usually 10 to 300 μm, preferably 20 to 200 μm. When the thickness of the base material for release material is 10 to 300 μm, it is possible to give the pressure-sensitive adhesive sheet or the like using the release material the stiffness and strength suitable for processing such as printing, cutting, and sticking.

In the case where a synthetic resin is used as the base material for the release material, the surface of the base material for the release material on which the release layer is to be formed may optionally be subjected to an oxidation process in order to improve the adhesion between the base material for the release material and the release layer. The surface can be treated by a method such as a roughening method or the like.
Examples of the oxidation method include corona discharge surface treatment, chromic acid surface treatment (wet), flame surface treatment, hot air surface treatment, ozone/ultraviolet irradiation surface treatment, and the like. In addition, examples of the roughening method include a sandblasting method, a solvent treatment method, and the like. These surface treatment methods are appropriately selected according to the type of the base material for the release material, but in general, the corona discharge surface treatment method is preferably used from the viewpoint of effectiveness and operability. A primer treatment can also be applied.

[Characteristics of adhesive sheet]
In the pressure-sensitive adhesive sheet of the present invention, the tunneling phenomenon hardly occurs at the interface between the pressure-sensitive adhesive layer and the release agent layer. Therefore, the adhesive layer is firmly protected by the release material until use.
Moreover, since the silicone compound does not migrate to the surface of the pressure-sensitive adhesive sheet base material, printing/printing defects and writing defects are less likely to occur when the surface is used as a printing/printing surface or as a writing surface.
In addition, the silicone compound does not migrate to the adhesive layer, and the reduction in tackiness of the adhesive layer that may occur due to migration of the silicone compound can be suppressed.
In addition, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention has both adhesiveness and releasability, which are contradictory properties. Therefore, during use, it does not come off easily even though it exhibits sufficient adhesiveness even on rough surfaces. Moreover, when the pressure-sensitive adhesive sheet is peeled off from the adherend, it can be peeled cleanly without leaving any adhesive residue on the adherend or damaging the adherend. In addition, it is also possible to repeat the sticking and peeling to the adherend.

<Peeling force>
In the pressure-sensitive adhesive sheet of one embodiment of the present invention, the release force of the release agent layer to the pressure-sensitive adhesive layer is adjusted to an appropriate level, so that the tunneling phenomenon at the interface between the release agent layer and the pressure-sensitive adhesive layer can be easily suppressed. The release force of the release agent layer to the pressure-sensitive adhesive layer is preferably 200-800 mN/25 mm, more preferably 300-600 mN/25 mm, still more preferably 330-550 mN/25 mm.
The peel strength can be measured by the method described in Examples below.

[Method for producing adhesive sheet]
<Manufacturing method of release material>
The method for producing the release liner of the pressure-sensitive adhesive sheet of the present invention is not particularly limited. Examples thereof include a method of laminating an agent layer to a release material substrate, and a method of coating a release material substrate with a solution prepared by adding a diluent solvent to the above-mentioned release agent composition so as to be coatable.
There is no particular limitation on the method of applying a solution prepared by adding a diluent solvent to the above-mentioned release agent composition so that the solution can be applied onto the release material substrate, and any known method can be used. Examples thereof include gravure coating, bar coating, spray coating, roll coating, die coating, knife coating, air knife coating, lip coating, and curtain coating.

Here, in the release agent layer formed from the above release agent composition, migration of the silicone compound to other layers does not occur. Therefore, the silicone compound does not migrate to the surface of the release liner substrate due to the contact between the release layer and the surface of the release liner substrate when the release liner is wound.

<Method for manufacturing adhesive sheet>
The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited. and bonding the release agent layer and the pressure-sensitive adhesive layer of the release material to produce the pressure-sensitive adhesive sheet.

The method for applying the aqueous solution of the pressure-sensitive adhesive composition onto the substrate for pressure-sensitive adhesive sheet is not particularly limited, and known methods can be used. Examples thereof include gravure coating, bar coating, spray coating, roll coating, die coating, knife coating, air knife coating, lip coating, and curtain coating.

Here, as described above, the silicone compound does not migrate to the release material substrate surface of the pressure-sensitive adhesive sheet of the present invention. Therefore, the silicone compound does not migrate to the pressure-sensitive adhesive sheet substrate due to contact between the surface of the release material substrate and the pressure-sensitive adhesive sheet substrate when the pressure-sensitive adhesive sheet is wound. Therefore, the pressure-sensitive adhesive sheet substrate does not adhere to the silicone compound, which may cause poor printing/printing or poor writing, and the printing/printing and writing conditions of the pressure-sensitive adhesive sheet substrate can be improved.

[Use of adhesive sheet]
According to the pressure-sensitive adhesive sheet of the present invention, the contradictory properties of adhesiveness and peelability are compatible. Therefore, during use, it does not come off easily even though it exhibits sufficient adhesiveness even on rough surfaces. Moreover, when the pressure-sensitive adhesive sheet is peeled off from the adherend, it can be peeled cleanly without causing adhesive residue on the adherend or damage to the adherend. In addition, it is also possible to repeat the sticking and peeling to the adherend.
Therefore, the pressure-sensitive adhesive sheet of one embodiment of the present invention can be used for management applications such as product management labels, process management labels, distribution management labels, etc. , stationery office supplies such as blind labels and fancy labels, advertising applications such as POP labels, and playground equipment applications.

The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.
In the following examples, "% by mass" means % by mass in terms of active ingredients with respect to the total amount of the composition.

[Physical properties]
Physical property values in the following examples and comparative examples are values measured by the following methods.

<Measurement of thickness of each layer>
It was measured using a constant pressure thickness measuring instrument manufactured by Teclock Co., Ltd. (model number: “PG-02J”, standard specifications: JIS K6783, Z1702, Z1709).
However, the thickness of the release agent layer was measured using a spectroscopic ellipsometer (manufactured by JA Woollam Japan Co., Ltd., trade name: Spectroscopic Ellipsometry 2000U).

[Examples and Comparative Examples]
The release materials of Examples 1-4 and Comparative Examples 1-2 were produced by the following procedure.

<Example 1>
As the non-silicone thermoplastic resin (A), an olefin-based polyethylene resin (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumikasen L-405) was used. In the following description, the polyethylene resin is also called "PE resin".
As the silylated polyolefin (B), a diluted product obtained by diluting a polyethylene-silicone-polyethylene triblock copolymer with polyethylene (manufactured by Mitsui Chemicals, Inc., trade name "EXFORA PE Masterbatch", silylated polyolefin content ratio: 30 mass %) was used. In the following description, the diluted product is also referred to as "Exfola".
In this example, the polyethylene used as the diluent contained in "EXFORA" was added as a component of the non-silicone thermoplastic resin (A).
A release agent composition was prepared by mixing 90 parts by mass of PE resin with 10 parts by mass of Exfora in a dry state.
Next, using the release agent composition, glassine paper (manufactured by Nippon Paper Industries Co., Ltd., trade name: Joshitsu Y-5K Seal 64.0G, thickness: 73 μm, basis weight: 64 g/m ² ) was used as a substrate for a release material. A release agent layer having a thickness of 20 μm was formed on the release agent substrate by extrusion processing by a lamination method to obtain a release agent.

<Examples 2 to 4>
A release material was obtained in the same manner as in Example 1, except that the blending amounts of the PE resin and Exphora in the release agent composition were changed as follows.
(Example 2)
・ PE resin: 83% by mass
・Exfora: 17% by mass
(Example 3)
・ PE resin: 75% by mass
・Exfora: 25% by mass
(Example 4)
・ PE resin: 30% by mass
・Exfora: 70% by mass

<Comparative Example 1>
A release material was obtained in the same manner as in Example 1, except that the release agent composition was prepared using only PE resin without blending Exfola.

<Comparative Example 2>
Addition type polyorganosiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KS835) 100 parts by weight was diluted with toluene to prepare a 10 wt% solution, and a platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: : PL-50T) was added to prepare a coating liquid of the release agent composition.
Next, the same glassine paper as in Example 1 was used as a base material for a release material, and a coating solution of a release agent composition was applied onto the base material for a release material. The coating amount was 1.0 g/m ² . Then, it was heat-dried at 150° C. for 1 minute to obtain a release material having a release agent layer with a thickness of 1 μm.

[Measurement and evaluation]
The following measurements and evaluations were carried out on the release materials of Examples 1-4 and Comparative Examples 1-2.

<Peel force measurement>
The release materials of Examples 1 to 4 and Comparative Examples 1 and 2 were attached to a removable adhesive label containing a spherical adhesive in the adhesive layer (manufactured by Lintec Co., Ltd., product name: Repeat 1720) with a 2 kg roller and adhered. got a sheet.
Then, after pressing for 3 hours at a pressure of 0.5 MPa, the peel force was measured when the release material was peeled off at a sample width of 25 mm, a peel speed of 300 mm/min, and a peel angle of 180°.

<Evaluation of Silicone Transfer Amount>
The release materials of Examples 1 to 4 and Comparative Examples 1 and 2 were cut into 15 cm×15 cm pieces, and a polyethylene terephthalate film (manufactured by Mitsubishi, trade name: Dia Wheel PET38T-100, 15 cm×15 cm) was placed on the release material surface. They were brought into contact and pressed at a pressure of 10 MPa for 24 hours. After the press was released, the amount of Si on the surface of the polyethylene terephthalate film that was in contact with the release material was measured using a fluorescent X-ray analyzer (manufactured by Rigaku Co., Ltd., desktop wavelength dispersive fluorescent X-ray analysis system "Mini-Z"). did.
Then, those in which the Si amount was below the detection limit (0.5 cps or less) were evaluated as no silicone transfer (○), and those in which the Si amount was above the detection limit (exceeding 0.5 cps) were evaluated as silicone transfer. Yes (x).

<Float of release material>
The pressure-sensitive adhesive sheet prepared for the peel force measurement was cut into a size of 150 mm×400 mm and used as a sample for evaluation of release material lift, and a polyethylene round bar with a diameter of 60 mm was prepared for evaluation.
With the adhesive sheet substrate side of the adhesive sheet sample as the inner surface and the release material side as the outer surface, the longitudinal direction of the sample was wound along the side surface of the round bar and fixed for 2 hours. After that, the sample was unwound and placed on a horizontal table with the pressure-sensitive adhesive sheet substrate side facing upward and the release material facing downward.
After 5 minutes, the state of the sample was observed, and the sample was rated as ◯ when the release material did not float (tunneling), and rated as x when it occurred.

Table 1 shows the results.

Table 1 shows the following.
From Comparative Example 1, when the release agent layer was formed only with the non-silicone thermoplastic resin (A), the transfer of the silicone to the adhesive layer and the lifting of the release agent were not observed, but the release force was too large. I understand.
Moreover, from Comparative Example 2, it is found that when the release agent layer is formed only from a silicone-based thermoplastic resin, the release force is too small, and the transfer of the silicone to the pressure-sensitive adhesive layer and the separation of the release agent are observed.
On the other hand, in Examples 1 to 4, the release force was adjusted to an appropriate range (200 to 800 mN/25 mm), and neither transfer of silicone to the adhesive layer nor lifting of the release material was observed. I understand.

1 Adhesive sheet 11 Base material for adhesive sheet 12 Adhesive layer 13 Release agent layer 14 Base material for release material 15 Release material

Claims (4)

A pressure-sensitive adhesive sheet having a laminated structure in which a pressure-sensitive adhesive sheet base material, a pressure-sensitive adhesive layer, a release agent layer, and a release material base material are laminated in this order,
The release agent layer is a layer formed from a release agent composition containing a non-silicone thermoplastic resin (A) as a main component and containing a silylated polyolefin (B),
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is a layer formed from a pressure-sensitive adhesive composition containing a spherical pressure-sensitive adhesive (C). The adhesive sheet according to claim 1, wherein the non-silicone thermoplastic resin (A) is an olefin resin (A1) other than the silylated polyolefin (B). The mass ratio (B/A) of the content of the silylated polyolefin (B) to the content of the non-silicone thermoplastic resin (A) is 1/99 to 30/70 according to claim 1 or 2. adhesive sheet. 4. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein a peel force when peeling the release agent layer from the pressure-sensitive adhesive layer is 200 to 800 mN/25 mm.

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