JPS6230174A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To provide a pressure-sensitive adhesive composition useful for wall paper, composed of a specific amount of a specific alkyl (meth)acrylate and a specific amount of an acrylic copolymer containing phosphorus atom and halogen atom other than fluorine atom and imparted with flame-retardancy without lowering the pressure-sensitive adhesivity. CONSTITUTION:The objective pressure-sensitive adhesive composition can be produced by copolymerizing a monomer containing phosphorus atom and/or halogen atom other than fluorine atom [e.g. trihalophenyl (meth)acrylate] to an acrylic copolymer containing >=40(wt)% alkyl (meth)acrylate having >=4C alkyl group (e.g. 2-ethylhexyl acrylate), and using the resultant acrylic copolymer as a main component. The content of the phosphorus atom and/or halogen atom other than fluorine atom in the copolymer is 0.5-30%, preferably 10-20%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pressure-sensitive adhesive composition, and in particular to improving the flame retardancy of a pressure-sensitive adhesive suitable for wallpaper.

(Prior art) Adhesive compositions include acrylic adhesives whose main component is acrylic esters of higher alkyl groups, rubber adhesives whose main component is natural rubber or synthetic rubber, urethane-based adhesives,
There are many adhesives such as vinyl ether type. However, among these adhesives, urethane-based adhesives have weak adhesive force and cohesive force, and lack so-called adhesive properties. Vinyl ether-based materials have the disadvantage of having many ether bonds and being photodegradable. For this reason, acrylic and rubber-based materials are currently mainly used. However, although acrylic and rubber adhesives have excellent adhesive properties, they are rather easily flammable from the standpoint of flame retardancy, so they cannot be made flame retardant in the same way as the support. desired.

A possible way to make the adhesive flame retardant is to add a flame retardant to the adhesive. However, this method tends to reduce the adhesive strength of the adhesive, which has a rather negative effect on the adhesive properties, and also causes problems such as migration of the flame retardant over time.

Therefore, the present inventors considered making the adhesive flame retardant by copolymerizing the adhesive with a flame retardant. However, in the case of rubber-based adhesives, it is difficult to copolymerize flame retardants with them, so in the present invention, flame retardation was specifically investigated for acrylic adhesives.

(Problems to be Solved by the Invention) The object of the present invention is to impart flame retardancy to an acrylic pressure-sensitive adhesive without reducing its adhesive properties.

(Means for Solving the Problem) As a result of intensive studies to achieve the above object, the present inventors have found that, in particular, acrylic resin containing 40% by weight or more of alkyl (meth)acrylate having an alkyl group having 4 or more carbon atoms. A monomer containing a halogen atom and/or a phosphorus atom other than a fluorine atom as a flame retardant component in a copolymer pressure-sensitive adhesive is added such that the content of the halogen atom and/or phosphorus atom is 0.5 to 30% by weight. It has been found that by copolymerizing in this manner, a pressure-sensitive adhesive having excellent flame retardancy can be obtained without deterioration of adhesive properties.

Specific examples of the alkyl (meth)acrylate having the above structure and having an alkyl group having 4 or more carbon atoms include 2-ethylhexyl acrylate, n-butyl acrylate, lauryl methacrylate, n-decyl methacrylate, etc. However, in the present invention, one or more of these are used as the main component, and if necessary, methyl methacrylate, styrene, ethyl (meth)acrylate, and cyclohexyl are used to increase the retention (cohesive) power of the adhesive. (Meth)acrylate, vinyl acetate, etc. are copolymerized. In this case, since adhesive strength and retention (cohesive) strength are contradictory physical properties, in order to maintain and balance both physical properties at a better level, acrylic acid, methacrylic acid, itaconic acid acid monomers such as 2-hydroxyethyl (meth)acrylate,
It is also possible to copolymerize functional group monomers such as glycidyl (meth)acrylate and N-methylol (meth)acrylamide, and cross-agents such as (poly)ethylene glycol di(meth)acrylate, divinylbenzene and diallyl phthalate.

In addition, in the above configuration, the acrylic adhesive has 4 carbon atoms.
The reason for using a material containing 40% by weight or more of alkyl (meth)acrylate having the above alkyl group is to maintain the desired adhesive strength.

In other words, even among acrylic adhesives, those whose main component is alkyl (meth)acrylate with a carbon number of 3 or less or those in which the amount of alkyl (meth)acrylate having an alkyl group with a carbon number of 4 or more is less than 40% by weight are Adhesive strength is weak
This is because even if flame retardant properties are imparted, it lacks adhesive strength in practical use.

In the structure of the present invention, monomers containing halogen atoms other than fluorine atoms and/or phosphorus atoms for imparting flame retardance by copolymerization to the adhesive include trihalophenyl (meth)acrylate, polyoxyethylene trihalogen Phenyl (meth)acrylate, 2.3 dihalopropyl (meth)acrylate, 2,6 dihalo 4-t-butylphenyl (meth)acrylate, 2-haloethyl (
meth)acrylate, vinyl chloride, vinylidene chloride, pentachlorophenyl (meth)acrylate, 3-halo 2-hydroxypropyl (meth)acrylate, mono
(2-Hydroxyethyl-α-haloacrylate) acid phosphate, 2-di(2-haloethyl)phosphate propyl acrylate, dimethyl phosphate ethyl acrylate, diethyl phosphate ethyl (
meth)acrylate, dibutyl phosphate ethyl (
meth)acrylate, mono (2-hydroxyethyl acrylate) acid phosphate, diphenyl 2
(Meth)acryloyloxyethyl phosphate and the like are exemplified.

The amount of these flame retardant imparting monomers cannot be determined uniformly because it varies depending on the degree of flame retardancy imparted to the adhesive (slow burning rate, self-extinguishing property) and adhesive performance, but the amount of halogen atoms in the adhesive and/or the total amount of phosphorus atoms is 0.5~
It is necessary to copolymerize to 30% by weight, preferably 10 to 20% by weight. Incidentally, if it is less than 0.5% by weight, flame retardancy cannot be imparted, and if it exceeds 30% by weight, the adhesive strength will decrease.

Note that the reason why fluorine atoms are excluded from the structure of the present invention is that they have poor effect as a flame retardant, and if used in large amounts, the adhesive properties of the adhesive will be reduced.

Thus, the adhesive composition of the present invention is prepared by adding an adhesive retention (cohesive) force enhancer, a cross agent, and a flame retardant monomer to the above-mentioned adhesive main components by a known polymerization method such as an emulsion polymerization method or a solution polymerization method. It is synthesized by copolymerization by legal, bulk polymerization, etc.

In the emulsion polymerization, anionic emulsifiers such as sodium alkyl sulfate and/or nonionic emulsifiers such as polyethylene glycol alkyl ether and polyethylene glycol alkyl phenyl ether can be used as the emulsifier. Further, as the solvent used in the solution polymerization, a halogenated solvent such as hexafluorometa-xylene, or a solvent such as methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, tetrahydrofuran, toluene, etc. is used alone or in combination.

Polymerization catalysts include hydrogen peroxide, benzoyl peroxide,
Also used are peroxides such as monobutyl peroxide, persulfates such as ammonium persulfate and potassium persulfate, and azo compounds such as azobisisobutyronitrile. Further, the degree of polymerization can be appropriately adjusted by adjusting the concentration of the polymerization catalyst, adjusting the polymerization temperature, and using a chain transfer agent.

The glass transition point of these polymers can be adjusted by selecting the above-mentioned monomer composition depending on the usage temperature range of the adhesive composition, and is usually in the range of -20°C to -60°C. adjusted to.

The pressure-sensitive adhesive composition of the present invention thus prepared contains crosslinking agents such as glyoxal, formaldehyde, amides, isocyanate i, and epoxy compounds, masking agents such as titanium oxide, surfactants such as antifoaming agents, and wetting agents. Various auxiliary agents known in the field of adhesives, such as, can be added.

Furthermore, when applying the adhesive composition to a substrate, it may be applied as is, but it can also be diluted with a solvent and applied, and examples of such solvents include solvents used in solution polymerization. Ru. When applied as an emulsion-type adhesive, the adhesive composition may be thickened by adding a thickener such as an alkali-thickened emulsion, sodium polyacrylate, polyvinyl alcohol, or hydroxyethyl cellulose. May be coated.

When applying the adhesive composition of the present invention to an adhesive sheet, a method is generally adopted in which the adhesive composition is applied to a separator and dried, and then a base material is laminated. It is also possible to laminate the separator after applying and drying the agent composition.

In the present invention, the support for applying the flame-retardant adhesive may include polyvinyl chloride, polyester,
Film sheets II and papers made of polystyrene, poly(meth)acrylic, polypropylene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, phenol resin, etc. are used.

Note that these base materials may be chlorinated.

The present invention will be described in detail below, but it goes without saying that the present invention is not limited to these examples. In addition,
Parts in the examples mean parts by weight.

Example 1 77 parts of 2-ethylhexyl acrylate, tribromphenyl acrylate) 2 (1, 3 parts of vinyl acetate, 1 part of acrylic acid, 0.1 part of n-dodecylmercaptan, 0.3 part of ethylene glycol dimethacrylate) The monomer mixture was subjected to emulsion polymerization using 2 parts of a mixed emulsifier of polyoxyethylene alkylphenyl sulfate/dioctyl sulfosuccinate to obtain an adhesive composition with a solids content of 50%. Manufactured by Mitsubishi Yuka Bardishu.

Add 2 parts of the product name "Latechol D"), adjust the pH of the system to 7 with aqueous ammonia, and adjust the viscosity (B-type viscometer) to 4000.
cps. This adhesive composition was applied to a polyethylene laminate release paper at a concentration of 20 g/m (solid content) and dried, and then bonded to a polyester film to form an adhesive sheet.

The degree of flame retardancy of this pressure-sensitive adhesive sheet was as shown in the table.

Example 2 Same as Example 1 except that a 7-mer mixture of 75 parts of 2-ethylhexyl acrylate, 20 parts of 2゜3-dibromopropylmethyl methacrylate, 5 parts of methyl methacrylate, and 2 parts of acrylic acid was used. A pressure-sensitive adhesive composition was obtained by copolymerization, and a pressure-sensitive adhesive sheet was obtained. The degree of flame retardancy of this pressure-sensitive adhesive sheet was as shown in the table.

Example 3 60 parts of 2-ethylhexyl acrylate, 25 parts of 2-chloroethyl acrylate, 5 parts of styrene, 2 parts of diphenyl
-A pressure-sensitive adhesive composition was obtained by copolymerization in the same manner as in Example 1, except that a monomer mixture of 10 parts of acryloyloxyethyl phosphate and 0.5 parts of acrylic acid was used, and a pressure-sensitive adhesive sheet was obtained. The degree of flame retardancy of this pressure-sensitive adhesive sheet was as shown in the table.

Example 4 Same as Example 1 except that a monomer mixture of 2-ethylhexyl acrylate (2-ethylhexyl acrylate) 806B, 10 parts of 2°4 dibrom-4.t-butylphenyl acrylate, 10 parts of cyclohexyl acrylate, and 1 part of acrylic acid was used. A pressure-sensitive adhesive composition was obtained by copolymerizing and a pressure-sensitive adhesive sheet was obtained. The degree of flame retardancy of this pressure-sensitive adhesive sheet was as shown in the table.

Comparative Example 1 A copolymerized adhesive composition was obtained in the same manner as in Example 1 except that a monomer mixture of 81 parts of 2-ethylhexyl acrylate, 15 parts of methyl methacrylate, 4 parts of vinyl acetate, and 1 part of acrylic acid was used, An adhesive sheet was obtained. The flammability of this adhesive sheet was as shown in the table.

Comparative Example 2 Adhesive copolymerized in the same manner as in Example 1 except that a monomer mixture of 72 parts of 2-ethylhexyl acrylate, 5 parts of methyl methacrylate, 15 parts of vinyl acetate, 8 parts of cyclohexyl acrylate, and 2 parts of acrylic acid was used. An adhesive composition was obtained, and a pressure-sensitive adhesive sheet was obtained. The flammability of this adhesive sheet was as shown in the table.

Comparative Example 3 Example 1 except that a monomer mixture of 81 parts of 2-ethylhexyl acrylate, 5 parts of methyl methacrylate, 5 parts of styrene, 10 parts of vinyl acetate, and 1 part of acrylic acid was used.
A pressure-sensitive adhesive composition was copolymerized in the same manner as above, and a pressure-sensitive adhesive sheet was obtained. The flammability of this adhesive sheet was as shown in the table.

Comparative Example 4 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that tribromphenyl methacrylate was changed to 0.8 parts and vinyl acetate was changed to 22 parts. The flammability of this adhesive sheet was as shown in the table.

Comparative Example 5 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that 59 parts of tribromphenyl methacrylate, 41 parts of 2-ethylhexyl acrylate, and 1 part of acrylic acid were used. The adhesiveness of this adhesive sheet was as shown in the table.

Evaluation of properties and adhesion Evaluation results (Note) The evaluation method for flame retardancy and adhesion is as follows.Flame retardancy evaluation method is based on JIS A-'1322.

After ignition under the conditions shown in the diagram above, combustibility is visually determined.

Preparation of Sample Four tack sheets with a width of 2 CI 11 and a length of 25 cm are stacked to form a sample for combustion.

・Tackiness evaluation method Adhesive force measurement method, according to JIS-Z-1538, 20
Adhesion strength when an adhesive sheet is pasted twice with a 2 kgO roller in a room at ℃ and 60% RH, and after 2 hours it is peeled off at a 180° angle using an Instron type tensile tester at a tensile speed of 300 m111/win. was measured.

Claims (1)

[Claims] Contains 40% by weight or more of an alkyl (meth)acrylate having an alkyl group having 4 or more carbon atoms, and has a content of halogen atoms other than fluorine atoms and/or phosphorus atoms of 0.
A flame-retardant pressure-sensitive adhesive composition comprising 5 to 30% by weight of an acrylic copolymer as a main component.