JPH03119086A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition excellent in cohesive force, initial tack, peel strength, weather resistance and water resistance by blending a polymer produced from an alkyl (meth)acrylate, a crosslinking component and a polymerization initiator with specified phosphoric esters. CONSTITUTION:An objective composition containing (A) a polymer produced from (i) an alkyl (meth)acrylate having 1-14C alkyl group, (ii) a crosslinking component and (iii) a polymerization initiator using as the raw materials and (B) one or more phosphoric esters represented by formulae I-III (R is H, 1-14C aliphatic hydrocarbon, benzyl, alpha-methylbenzyl or nonylphenyl; R' is 2-4C alkylene; l, m and n are integer of 0-20).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an acrylic pressure-sensitive adhesive composition widely used for labels, tapes, etc. More specifically, an acrylic pressure-sensitive adhesive composition with outstanding pressure-sensitive adhesion ability obtained by adding a small amount of a phosphate ester-based tackifier to an acrylic pressure-sensitive adhesive composition obtained by a radical polymerization method. relating to things.

[Prior art] Acrylic pressure-sensitive adhesives have superior physical properties such as oil resistance and weather resistance compared to natural rubber-based or synthetic rubber-based adhesives, but on the other hand, they do not contain crosslinking components, etc. (In this specification, these are simply referred to as "(meth)acrylic esters.")
Pressure-sensitive adhesives obtained by the radical polymerization method have insufficient cohesive force when a high degree of cohesive force is required, that is, when used under large stress or at high temperatures. Therefore, in the past, copolymerizable monomers that give polymers with a high glass transition point, monomers with crosslinkable functional groups, crosslinking components such as epoxy resins, isocyanates, melamine resins, urea resins, and amino resins were used as (meth)acrylic acid esters. Attempts have been made to increase the cohesive force by polymerizing the mixture.

However, although it is possible to improve the cohesive force by adding such copolymerizable monomers and crosslinking components, a new problem arises: a decrease in the initial adhesive force, which is a property contradictory to the cohesive force. Therefore, in order to compensate for this decrease in adhesive strength and further adjust the balance of cohesive strength, peel strength, initial adhesive strength, etc., methods have been taken such as adding low molecular weight tackifiers to pressure-sensitive adhesives. .

However, determining the formulation requires skill, and there are problems such as slight differences in the amount added or the composition of the base acrylic adhesive can significantly vary the performance of the prepared pressure-sensitive adhesive. There is.

Furthermore, since these additives are added in a large amount of 10 to 20 parts by weight per 100 parts by weight of the solid content, the additives cause deterioration in weather resistance, water resistance, etc. of the pressure sensitive adhesive.

[Problems to be Solved by the Invention] An object of the present invention is to provide an acrylic pressure-sensitive adhesive having excellent cohesive force, initial adhesive strength, peel strength, weather resistance, water resistance, and the like.

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors have added a (meth)acrylic polymer obtained by polymerizing a (meth)acrylic acid ester and a crosslinking component to a (meth)acrylic polymer. The present inventors have discovered that adding a very small amount of a phosphate ester tackifier with excellent solubility can produce excellent results, leading to the completion of the present invention.

That is, the present invention provides an alkyl group having 1 to 14 carbon atoms (
A polymer obtained by polymerizing a meth)acrylic acid alkyl ester, a crosslinking component, and a polymerization initiator, and a polymer obtained by the following formula (wherein, R is hydrogen or an aliphatic hydrocarbon group having 1 to 14 carbon atoms, a benzyl group, α- Represents a methylbenzyl group or a nonylphenyl group, Ro represents an alkylene group having 2 to 4 carbon atoms, and σ, m, and n represent integers of θ to 20. A pressure sensitive adhesive composition is provided.

The above (meth)acrylic acid alkyl ester has an alkyl group with a carbon number of 1-1 from the viewpoint of adhesive properties after polymerization, etc.
14 (meth)acrylic acid alkyl ester. Specifically, acrylic acid alkyl esters include butyl acrylate, 2-ethylhexyl acrylate, ethyl acrylate, octyl acrylate, etc., and methacrylic acid alkyl esters include methyl methacrylate, ethyl methacrylate, and methacrylic acid. Examples include butyl, dodecyl methacrylate, and the like. Also, a mixture of these may be used.

The above-mentioned crosslinking component determines the gel fraction of the polymer and functionally adjusts the retention force. Specifically, polyfunctional monomers such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane triacrylate, methylenebisacrylamide, triallylisocyanate, divinylbenzene, etc. , mono- or polyepoxy group-containing monomers such as glycidyl methacrylate, allyl glycidyl ether, 1,3-butadiene epoxide, ethylene glycol diglycidyl ether, etc. and polycarboxylic acids such as glutaric acid, adipic acid, maleic acid, fumaric acid, etc. Examples include combinations with acids and the like.

The polymerization initiator is not particularly limited, but includes those commonly used in radical polymerization, such as peroxides such as benzoyl peroxide, persulfates such as potassium persulfate and ammonium persulfate, and 2.2° azobis(2-amidino). Azo compounds such as (propane) dihydrochloride and 2°2° azobisisobutyronitrile are preferred, and may be used depending on the polymerization method such as solution polymerization method or emulsion polymerization method.

The polymerization of the present invention is preferably radical polymerization, and the above (meth)
An alkyl acrylate ester, a crosslinking component, and a polymerization initiator are used as polymerization raw materials, or a monomer that can be further copolymerized with an alkyl (meth)acrylate ester (hereinafter referred to as "copolymerizable monomer") By adding as a polymerization raw material, the balance of cohesive force, initial tackiness, peel strength, etc. of the adhesive is further improved.

The above-mentioned copolymerizable monomer is one whose polymer has a high glass transition point. Specifically, carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, etc., nitrile group-containing monomers such as acrylonitrile, methacrylonitrile, etc.
Other examples include vinyl acid, styrene, and mixtures thereof.

Furthermore, during solution polymerization, an inert solvent may be added as a diluent for purposes such as viscosity adjustment. Specific examples include single solvents such as toluene, ethyl acetate, and THE, and mixed solvents thereof. During emulsion polymerization, a small amount of an anionic surfactant such as sodium dodecyl sulfate or a nonionic surfactant such as polyoxyethylene nonylphenyl ether may be added for the purpose of improving polymerization stability.

In the composition of the above polymerization raw material, the amount of the crosslinking component used is 0.5 to 20 parts by weight, preferably 3 to IO parts by weight, based on 100 parts by weight of the (meth)acrylic acid alkyl ester. If it is outside the above range, it will be difficult to control the polymerization stability and gel fraction ratio, which is not preferable. The amount of the polymerization initiator used is 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the (meth)acrylic acid alkyl ester. If the amount is less than 0.05 part by weight, the polymerization rate will be significantly reduced, and the molecular weight of the polymer will become too large, resulting in a decrease in initial tackiness and making it unsuitable as an adhesive. On the other hand, if the amount is more than 2 parts by weight, the molecular weight of the polymer decreases and the peel strength decreases, making it unsuitable as an adhesive. Further, the amount of the copolymerizable monomer to be used can be up to 100 parts by weight per 100 parts by weight of the (meth)acrylic acid alkyl ester, but is preferably 5 to 50 parts by weight. If the amount exceeds 100 parts by weight, the glass transition point increases and the adhesiveness decreases, which is not preferable. In addition, the solvent used during solution polymerization is (
It is preferably 50 to 200 parts by weight based on 100 parts by weight of the alkyl meth)acrylate. In addition, since the surfactant used during emulsion polymerization affects the water resistance of the resulting adhesive, it is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the (meth)acrylic acid alkyl ester.
The amount of water used is also preferably 50 to 200 parts by weight per 100 parts by weight of the (meth)acrylic acid alkyl ester.

As a polymerization method, a homogeneous mixture of the above (meth)acrylic ester and crosslinking component may be added dropwise to an inert solvent or surfactant aqueous solution in which a polymerization initiator is dissolved, and polymerization may be carried out. Alternatively, in crosslinking using a monomer having a crosslinkable functional group, either a monomer having an epoxy group or a monomer having a carboxyl group is copolymerized with the above (meth)acrylic acid ester, etc. After that, a method of crosslinking by adding a polycarboxylic acid or a polyepoxide compound may be adopted. Further, the (meth)acrylic polymer obtained by any of the above polymerization methods may be polymerized with further addition of another crosslinking component.

The polymerization conditions in the above polymerization are appropriately selected depending on each of the above polymerization methods, but usually the polymerization temperature is 60 to 90°C and the polymerization time is 2.
~6 hours.

The (meth)acrylic polymer used in the adhesive composition of the present invention obtained as described above has a glass transition temperature of 210
~260°C. Desired adhesion cannot be obtained outside this temperature range.

In the pressure-sensitive adhesive composition of the present invention, the reaction product mixture obtained by the above polymerization is added as a tackifier to the above formulas (1) to (
It is prepared by adding one or more phosphoric esters represented by I[[). The amount added is 0.65 to 15 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of polymer solids in the reaction product mixture.

If the amount is less than 0.5 parts by weight, the desired initial adhesive strength cannot be obtained, and if it is more than 15 parts by weight, the weather resistance, water resistance, etc. of the adhesive will deteriorate, which is not preferable.

In the method for synthesizing the phosphoric acid esters (1) to (III) above, for example, the sesquiphosphate added with 1.1 mol of α-methylbenzylphenol ethylene oxide is prepared by adding 1.1 mol of α-methylbenzylphenol ethylene oxide to the adduct under a nitrogen atmosphere. It is synthesized by adding niline pentoxide over 2 hours at 80 to 100°C and further aging for 6 hours.

Furthermore, the pressure-sensitive adhesive composition of the present invention may contain conventionally known additives such as colorants, fillers, anti-aging agents, viscosity-adjusting diluents, etc., if necessary, and the amount of additives to be added is within the range normally used. The amount you can afford is fine. Furthermore, if greater cohesive force or initial tackiness is required, a known crosslinking agent or tackifier may be added as necessary to the extent that the characteristics of the present invention are not impaired.

[Examples] The present invention will be specifically explained below using Examples, but the present invention is not limited to these Examples. still,
In the following formulations, parts mean parts by weight.

Synthesis Reference Example 1 of Phosphate Ester (Synthesis of Sesquiphosphate Added with 1.1 Moles of α-Methylbenzylphenol Ethylene Oxide) α-Methylbenzylphenol Ethylene Oxide 1.
1 mole adduct 105. 14.2 g (0.1 mol) of niline pentoxide was added to Ig (0.3 mol) at 80 to 100°C under a nitrogen stream over 2 hours, and the mixture was further aged for 6 hours. After the by-product pyro compound was decomposed by adding water (20 g), excess water was removed to obtain a sesquiphosphate with 1.1 mol of α-methylbenzylphenol ethylene oxide added.

Reference Example 2 (Synthesis of nonyl phenyl ether ethylene oxide 3 mol adduct sesquiphosphate) 85.3 g of nonylphenol ethylene oxide 3 mol adduct (0,
3 mol) and 14.2 g (0.1 mol) of niline pentoxide were reacted under the same conditions as in Reference Example 1 to obtain a sesquiphosphate added with 3 mol of nonylphenol ethylene oxide.

Reference Example 3 (Synthesis of octylphenol triphosphate) To 61.9 g (0.3 mol) of octylphenol was added 15.3 g (0.3 mol) of phosphorus oxychloride at 100°C to 130°C under a nitrogen stream.
, 1 mol) was added over 1 hour. Hydrogen chloride generated during synthesis is absorbed into an aqueous sodium hydroxide solution.
After aging at 120°C for 5 hours, the temperature was raised to 135°C and 0.
Octylphenol triphosphate was obtained by aging for 5 hours.

Manufacturing example of pressure sensitive adhesive composition! After purging a 50Q 17 reaction vessel equipped with a thermometer, stirring rod, cooling tube, and nitrogen introduction tube with nitrogen, 100 parts of toluene was added, and the mixture was heated to 80° C. under a nitrogen stream.

After reaching the above temperature, a solution of 0.2 parts of benzoyl peroxide as a polymerization initiator dissolved in 10 parts of toluene was added.

Next, a monomer mixture consisting of 60 parts of 2-functional tylhexyl acrylate, 60 parts of butyl acrylate, 10 parts of acrylic acid, 3 parts of glycidyl acrylate, and 25 parts of styrene was added dropwise over 3 hours, and after the addition was completed, the mixture was heated and stirred for another 2 hours. did.

After cooling to room temperature, 1.1 mol of α-methylbenzylphenol ethylene oxide obtained in Reference Example 1 was added as a phosphate ester tackifier, and 3 parts of sesquiphosphate was added to 100 parts of the solid content of the polymer to make it pressure sensitive. An adhesive composition was obtained. The pressure sensitive adhesive composition thus obtained had a solids content of 59.8% and a glass transition point of 244.

Examples 2 to 5 and Comparative Examples 1 to 4 Pressure-sensitive adhesive compositions were produced in the same manner as in Example 1, except that the tackifier shown in Table 1 was used.

The physical properties (peel strength, holding power, initial adhesive strength, and water resistance) of the pressure-sensitive adhesive compositions obtained in Examples 1 to 5 and Comparative Examples 1 to 4 above were tested, and the results are shown in Table 1. Shown below.

■): Harinister P2, manufactured by Yokoma Kasei Kogyo Co., Ltd.: Tackirol EP303, manufactured by Izuru Kagaku Kogyo Co., Ltd.): Finton D1004, manufactured by Nippon Zeon Co., Ltd. A pressure-sensitive adhesive composition was applied to a PET film with a width of +25 mm, and the thickness after drying was 30 μm.
After drying at room temperature, it was heat-treated at 105℃ for 10 minutes, and a new PET film was attached with a load of 5kg and peeled off at 180 degrees and a peeling speed of 5cx/min, and its peel strength (9/ 25 iIm) was measured. A large value indicates a large covering adhesive force.

5): Make a pressure sensitive adhesive tape in the same way as the peel strength test, and
It was attached to a ferro plate with an adhesive area of 5 mm x 25 mm, and the time until it fell was measured at 20° C. or 60° C. under a load of I kg. The longer the time, the greater the holding force.

6): Indicated by the value of ball number according to the ball rolling test method by J.DoW method. The larger the ball number, the greater the initial adhesive force.

7): Apply a pressure-sensitive adhesive onto the release paper so that the thickness after drying is 30 μm, and after drying at room temperature,
Heat treatment was performed for 5 minutes. This pressure-sensitive adhesive was transferred to paper, wrapped around a 2011Illlφ polyethylene cylindrical rod with a width of 25IIIn, and immersed in water at 20°C for 5 minutes.
The peeling rate (%) after 1 day was measured. The smaller the number, the better the water resistance.

[Effects of the invention] As can be seen from the results in Table 1, the acrylic pressure-sensitive adhesive composition of the present invention does not contain conventionally used rosin-based, phenolic resin-based, or petroleum resin-based tackifiers. It has particularly excellent peel strength, holding power, initial adhesive strength, and water resistance compared to other products.

Claims (2)

[Claims] (1) A polymer obtained by polymerizing a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms, a crosslinking component, and a polymerization initiator, and the following formula ▲ Numerical formula, chemical formula, table, etc. ▼ ( I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) and ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, R is hydrogen or an aliphatic hydrocarbon group having 1 to 14 carbon atoms, benzyl group, α-methylbenzyl group or nonylphenyl group, R' represents an alkylene group having 2 to 4 carbon atoms, and l, m, and n represent integers of 0 to 20. A pressure-sensitive adhesive composition containing one or more types. (2) Claim 1, wherein the polymerization is carried out by further adding a monomer copolymerizable with the (meth)acrylic acid alkyl ester.
The pressure sensitive adhesive composition described.