JP2516018B2 - Pressure sensitive adhesive - Google Patents

Description

TECHNICAL FIELD The present invention is excellent in miscibility between an acrylic pressure-sensitive adhesive and a silicone pressure-sensitive adhesive, has good liquid permeation-preventing property, and has good adhesiveness to a low energy surface. It relates to a pressure sensitive adhesive.

Related Art and Problems Acrylic pressure-sensitive adhesives have the advantage that adhesive properties such as adhesive force and cohesive force can be controlled appropriately by changing the monomers used and the compounding composition, while using polyolefins such as polyethylene and polypropylene. Poor adhesion to low-energy surfaces such as silicone, and liquids such as water that easily penetrate into the interface with the adherend, which can lead to problems such as reduced adhesion and peeling. Has been pointed out.

Therefore, although it has been a conventional problem to overcome the disadvantage while utilizing the advantage thereof, the present inventors have found that the purpose can be achieved by using a silicone-based pressure-sensitive adhesive together.

However, the acrylic pressure-sensitive adhesive and the silicone pressure-sensitive adhesive are poorly miscible and easily phase-separated, which reduces the cohesive force of the pressure-sensitive adhesive, and thus the pressure-sensitive adhesive that can be put to practical use is not available. There was a problem that was difficult to obtain.

As an attempt to solve the problem of phase separation between acrylic pressure-sensitive adhesive and silicone pressure-sensitive adhesive, crosslinking of peroxide, lead octoate, etc. was carried out in order to obtain a pressure-sensitive adhesive that can be easily peeled off. A product obtained by co-crosslinking with an agent has been proposed (JP-A-59-145269). However, in order to prevent the phase separation of both pressure-sensitive adhesive components and to express a satisfactory cohesive force, it is necessary to perform co-crosslinking treatment at high temperature (100 to 150 ° C) for a long time (5 to 10 minutes). Therefore, the pressure-sensitive adhesive obtained is poor in tackiness, and in the case of the re-peelable type, it is particularly difficult to apply for the purpose of the present invention.

Means for Solving the Problems The present inventors have overcome the problems of phase separation of both pressure-sensitive adhesives described above, and have maintained the advantages of acrylic pressure-sensitive adhesives while overcoming their disadvantages. As a result of earnest studies for developing an adhesive, the inventors have found that the purpose can be achieved by using a special graft copolymer, and have completed the present invention.

That is, the present invention is a pressure-sensitive adhesive characterized by containing a silicone / acrylic graft copolymer containing a silicone macromonomer as a component, an acrylic pressure-sensitive adhesive, and a silicone pressure-sensitive adhesive. Is provided.

Action Until now, the combined use of acrylic pressure-sensitive adhesives and silicone pressure-sensitive adhesives has caused problems such as loss of tackiness due to phase separation and peeling and adhesive residue due to a decrease in cohesive force, and is not suitable for practical use. It has been regarded as a representative example of something that does not exist.

However, by blending the silicone-acrylic graft copolymer, the miscibility is remarkably improved,
Even when the silicone pressure-sensitive adhesive is rich with respect to the acrylic pressure-sensitive adhesive, a stable mixed system is formed, and problems such as peeling and adhesive residue due to phase separation do not occur.

Examples of Components of the Invention In the present invention, known acrylic pressure-sensitive adhesives can be used. As a typical example thereof, an ester such as acrylic acid or methacrylic acid using a primary or secondary alcohol having 1 to 14 carbon atoms as a main component, and a monomer having a functional group such as a carboxyl group or a hydroxyl group, Weight average molecular weight of 300,000 or more, especially 300,000-10, obtained by copolymerizing modified monomers such as styrene, vinyl acetate and acrylonitrile.
Something like, 000,000.

Also, known silicone-based pressure-sensitive adhesives can be used. As a typical example, it is composed of a SiO ₂ unit and an R ₃ SiO _0.5 unit (wherein R is a substituted or unsubstituted monovalent hydrocarbon group such as a methyl group, an ethyl group, a phenyl group and a vinyl group). Examples thereof include those obtained by condensing a copolymer and a polysiloxane having a hydroxyl group, a vinyl group or the like at the end of the molecular chain and having an R ₂ ′ SiO unit (where R ′ is the same as the above R). To be

In the present invention, the amount of the silicone pressure-sensitive adhesive used is
10 to 150 parts by weight per 100 parts by weight of the acrylic pressure sensitive adhesive is suitable. If the amount used is less than 10 parts by weight, the combined effect will be poor and the adhesive force to the low energy surface will not be improved satisfactorily. If it exceeds 150 parts by weight, the adhesive properties of the acrylic pressure-sensitive adhesive will be impaired.

The pressure-sensitive adhesive of the present invention improves the miscibility of both pressure-sensitive adhesives by using a silicone / acrylic graft copolymer.

As the silicone / acrylic graft copolymer, those containing a silicone macromonomer and a grafting monomer as components are used.

As the silicone macromonomer, a radical polymerizable one is usually used. This is composed of a polymer having a relatively low molecular weight having a polymerizable functional group at one end of the molecular chain, and its preferable molecular weight is 3,000 to 50,000 based on the polymerization average molecular weight. If the molecular weight is less than 3,000, the pressure-sensitive adhesive obtained may be poorly miscible.
If it exceeds 000, the reactivity may be lowered and it may be difficult to obtain the intended silicone-acrylic graft copolymer.

The silicone macromonomer is prepared, for example, by reacting a living polymer obtained by anionic polymerization of a cyclic siloxane represented by the following general formula A with a radical polymerizable silicone compound represented by the general formula B (living polymerization termination reaction). ) Can be carried out (JP-A-59-126478). In addition, the amount of the radically polymerizable silicone compound used in the preparation is preferably an amount such that 1 to 5 equivalents of Si—Cl in the compound are present with respect to 1 equivalent (1 mol) of the living polymerization initiator.

General formula A: (Wherein, R ¹ is methyl group, an ethyl group or a phenyl group, p is 3 or 4.) General formula ^{_{B: CH 2 = CR 2 -COOCH}} 2 I O M C 3 H 6 -Si (Cl)
_n (R ³ ) _3-n or (However, R ² is hydrogen or a methyl group, R ³ and R ⁴ are a methyl group, an ethyl group or a phenyl group, m is 0 or 1, and n is an integer of 1 to 3. l when m = 0
= 0, 1 or 2, and when m = 1, l = 2. In the synthesis of living pommers by anionic polymerization of the cyclic siloxane represented by the general formula A, known anionic polymerization initiators such as alkali metal hydroxides, alkoxides or silanolates, preferably organic lithium compounds are used. It can be easily carried out according to a conventional method such as a bulk polymerization method or a solution polymerization method. Specific examples of the cyclic siloxane include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, hexaethylcyclotrisiloxane, octaethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane, octaphenylcyclotetrasiloxane, and the like. Hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane are preferably used in view of availability and ease of polymerization.

On the other hand, the radical polymerizable silicone compound represented by the general formula B can be easily synthesized by a known method. For example, in the case of the compounds of the formula the former ^{_{formula: CH 2 = CR 2 -COOCH 2}} I O m CH 2 CH = CH 2 ( provided that, R ^2, l, m are as defined above.) In Obtained by a hydrosilylation reaction between an unsaturated acrylic acid ester represented by the formula and a compound represented by the formula: HSi (Cl) _n (R ³ ) _3-n (wherein R ³ and n are the same as above). be able to.

As another method for preparing the silicone macromonomer, a method in which a silicone represented by the following general formula C and an acrylic compound represented by the following general formula D are subjected to dehydrochlorination reaction or dealcoholization reaction to obtain a modified silicone (JP-A-58-154766 and JP-A-59-20360).
The amount of the acrylic compound used in the preparation is appropriately 0.25 to 1 mol per mol of silicol.

General formula C: (However, R ⁵ and R ⁶ are a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, a phenyl group or a monovalent halogenated hydrocarbon group, and n is an integer of 1 or 2 or more.) General formula D: (However, n is an integer of 1 to 3, R ⁷ is hydrogen or a methyl group, R ⁸ is a methyl group, an ethyl group or a phenyl group, and X is a chlorine, a methoxy group or an ethoxy group.) The synthesis of the acrylic compound represented by the general formula D is
For example, it can be carried out by reacting a compound having an aliphatic multiple bond with a silicon compound in the presence of chloroplatinic acid. Specific examples of the acrylic compound include γ-
Methacryloxypropyltrichlorosilane, γ-methacryloxypropylmethyldichlorosilane, γ-methacryloxypropylethyldichlorosilane, γ-methacryloxypropylphenyldichlorosilane, γ-methacryloxypropylmethylchlorosilane, γ-methacryloxypropyldiethylsilane, γ -Methacryloxypropyldiphenylchlorosilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyldimethylmethoxysilane, γ-
Methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-
Methacryloxypropyl dimethylethoxysilane, γ
-Acryloxypropyltrichlorosilane, γ-acryloxypropylmethyldichlorosilane, γ-acryloxypropyldimethyldichlorosilane and the like. In the present invention, those having 1 or 3 chlorine, methoxy group or ethoxy group (X) are preferably used.

The target silicone macromonomer prepared as described above, in which silicol is introduced into one molecule of an acrylic compound, is an acrylic polyfunctional silicol produced as a by-product (two or more molecules of acrylic compound are introduced into one molecule of silicol). Etc.) and unreacted starting material silicol, but can be used as they are in the present invention.

In order to obtain the silicone-acrylic graft copolymer used in the present invention, as the grafting monomer to be reacted with the silicone macromonomer, an acrylic acid ester and, if necessary, other radical copolymerizable monomers are used. In the present invention, from the viewpoint of compatibility with the acrylic pressure-sensitive adhesive, it is appropriate to use 50% by weight or more of acrylic acid ester as the grafting monomer component.

Examples of the acrylic acid ester used include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a 2-ethylhexyl group, an isooctyl group, an isononyl group, an isodecyl group, and the like having 30 or less carbon atoms. Examples thereof include esters such as acrylic acid or methacrylic acid having an alkyl group of 14 or less.

On the other hand, other radical copolymerizable monomers used as needed include acrylic acid, methacrylic acid, styrene,
Examples thereof include vinyl acetate and acrylonitrile.

The silicone / acrylic graft copolymer used in the present invention is appropriately determined according to the molecular weight and blending ratio of the silicone pressure sensitive adhesive or acrylic pressure sensitive adhesive used in combination, and is not particularly limited. Generally prepared using 1 to 30 parts by weight of the silicone macromonomer per 100 parts by weight of the grafting monomer, the weight average molecular weight of 20,0
It is preferably 00 or more, especially 20,000 to 2,000,000. If the amount of the silicone macromonomer used is less than 1 part by weight, the resulting graft copolymer will have a poor compatibility effect.
When it exceeds the weight part, the copolymerizability is lowered and unreacted silicone macromonomer is apt to remain. On the other hand, if the weight average molecular weight of the graft copolymer is less than 20,000, compatibility is poor.

The amount of the silicone-acrylic graft copolymer used is appropriately 0.5 to 30 parts by weight, based on 100 parts by weight of the total amount of the acrylic pressure-sensitive adhesive and the silicone-based pressure-sensitive adhesive,
1 to 25 parts by weight is preferable. If the amount used is less than 0.5 part by weight, the compounding effect will be poor, and if it exceeds 30 parts by weight, the pressure-sensitive adhesive obtained will have poor adhesive properties, which is not preferred.

The pressure-sensitive adhesive of the present invention can be obtained by mixing an acrylic pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and a silicone-acrylic graft copolymer.

The pressure-sensitive adhesive of the present invention may contain a compounding agent such as a pigment, a tackifying resin, a plasticizer or a curing agent, which is usually added to the pressure-sensitive adhesive. These compounding agents are generally used in the case of not being used together from the viewpoint of compatibility in the case of a single type of silicone pressure sensitive adhesive, but in the present invention, the acrylic pressure sensitive adhesive and the silicone / acrylic graft copolymer are used together. Since the polymer is used in combination, it can be optionally used.

Then, by using it, it becomes possible to more easily control the adhesive property and the like of the pressure-sensitive adhesive.

EFFECTS OF THE INVENTION According to the present invention, since the silicone / acrylic graft copolymer is used, a pressure-sensitive adhesive having excellent miscibility, which comprises a mixture of a silicone-based pressure-sensitive adhesive and an acrylic pressure-sensitive adhesive, can be obtained. it can.

Further, the pressure-sensitive adhesive of the present invention retains the advantage of the acrylic pressure-sensitive adhesive that the adhesive property can be controlled by adding a compounding agent, and has a low energy which cannot be achieved by the acrylic pressure-sensitive adhesive alone. It also has good adhesion to the surface and prevention of liquid penetration.

Example Reference Example 1 (acrylic pressure-sensitive adhesive) 80 parts of butyl acrylate (parts by weight, the same applies hereinafter), 18 parts of butyl methacrylate, and 2 parts of 2-hydroxyethyl methacrylate were mixed with 150 parts of toluene. 5 parts at 70 ° C. in the presence of 0.3 parts benzoyl oxide, then 0.2 parts benzoyl peroxide
Additional parts were added and copolymerized at 75 ° C. for 3 hours to obtain a toluene solution of an acrylic pressure-sensitive adhesive.

Reference Example 2 (Silicone pressure sensitive adhesive) R ₃ SiO _0.5 unit and SiO ₂ unit (former / latter molar ratio 0.5 /
50 parts of a siloxane resin composed of 1) and 50 parts of a raw rubber-like diorganopolysiloxane composed of R ₂ ′ SiO units are subjected to a condensation reaction, 5 mol% of all organic groups are phenyl groups, and 0.3 mol% are vinyl groups. Thus, a 60% by weight xylene solution of a pressure-sensitive adhesive consisting of organopolysiloxane with the rest being methyl groups was obtained.

Reference Example 3 (Silicone / Acrylic Graft Copolymer) 100 parts of α, ω-dihydroxydimethylpolysiloxane (average degree of polymerization of about 30), 3 parts of γ-methacryloxypropyltrimethoxysilane, and 1 part of potassium acetate The reaction was performed under a nitrogen stream at 150 ° C. for 24 hours, the obtained product was poured into 400 parts of toluene, and this was filtered to remove potassium acetate.

Next, 20% by weight of the silicone macromonomer obtained above
To 100 parts of a toluene solution, 70 parts of butyl acrylate, 30 parts of butyl methacrylate, 1 part of 2,2'-azobisisobutyronitrile and 100 parts of toluene were added, and the mixture was heated at 70 ° C for 6 hours.
Then, the mixture was polymerized at 80 ° C for 3 hours to give a polymerization average molecular weight of 100,00.
A 40 wt% toluene solution of the silicone / acrylic graft copolymer of 0 was obtained.

Example 1 80 parts of the acrylic pressure-sensitive adhesive of Reference Example 1 (solid content, the same hereinafter), 20 parts of the silicone-based pressure-sensitive adhesive of Reference Example 2,
Silicone / acrylic graft copolymer 2 of Reference Example 3
Parts and 0.5 parts of a polyisocyanate-based crosslinking agent were mixed to obtain a pressure-sensitive adhesive.

Example 2 60 parts of the acrylic pressure-sensitive adhesive of Reference Example 1, 40 parts of the silicone-based pressure-sensitive adhesive of Reference Example 2, 5 parts of the silicone-acrylic graft copolymer of Reference Example 3, and a polyisocyanate-based adhesive A pressure sensitive adhesive was obtained by mixing 0.5 part of a crosslinking agent.

Example 3 50 parts of the acrylic pressure-sensitive adhesive of Reference Example 1, 50 parts of the silicone-based pressure-sensitive adhesive of Reference Example 2, 20 parts of the silicone-acrylic graft copolymer of Reference Example 3, and a polyisocyanate-based adhesive A pressure sensitive adhesive was obtained by mixing 0.5 part of a crosslinking agent.

Example 4 35 parts of the acrylic pressure-sensitive adhesive of Reference Example 1, 65 parts of the silicone-based pressure-sensitive adhesive of Reference Example 2, 25 parts of the silicone-acrylic graft copolymer of Reference Example 3, and a polyisocyanate-based adhesive A pressure sensitive adhesive was obtained by mixing 0.5 part of a crosslinking agent.

Comparative Example 1 A pressure-sensitive adhesive was obtained in the same manner as in Example 2 except that the silicone / acrylic graft copolymer was not added.

Comparative Example 2 The blending amount of the silicone-acrylic graft copolymer was
A pressure-sensitive adhesive was obtained in the same manner as in Example 2 except that the amount was 40 parts.

Evaluation test The pressure-sensitive adhesives obtained in Examples and Comparative Examples were applied on a 25 μm-thick polyester film so that the thickness after drying would be 25 μm, and dried at 80 ° C. for 5 minutes to give a pressure-sensitive adhesive sheet. It was produced and subjected to the following test.

[Adhesive strength] ST plate (stainless steel plate SUS304) or at 23 ° C and 65% RH
The 180 degree peeling adhesive strength to a PP plate (polypropylene plate) was measured by an Instron type universal testing machine under the condition of a tensile speed of 300 mm / min.

[Holding power] In accordance with JIS Z 0237, the holding power (time until falling) on the stainless steel plate at 40 ° C was examined. The load applied was 1 kg.

[Water immersion] Stick an adhesive sheet on a glass plate (bonding area 30 mm x 50 m
m), soaked in 60 ° C warm water for 72 hours, then taken out and inspected visually for water infiltration. ○: Abnormal, ○: partial inundation: △, fully flooded or adhesive sheet It was evaluated as × when peeled.

The results are shown in the table.

Claims (3)

(57) [Claims] 1. A pressure-sensitive adhesive containing a silicone-acrylic graft copolymer containing a silicone macromonomer as a component, an acrylic pressure-sensitive adhesive, and a silicone pressure-sensitive adhesive. 2. The content of the silicone / acrylic graft copolymer is 0.5 to 30 parts by weight per 100 parts by weight of the total amount of the acrylic pressure sensitive adhesive and the silicone pressure sensitive adhesive. The pressure-sensitive adhesive according to item 1. 3. The pressure sensitive adhesive according to claim 1, wherein the content of the silicone pressure sensitive adhesive is 10 to 150 parts by weight per 100 parts by weight of the acrylic pressure sensitive adhesive.