JPH0224379A - Pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To provide a pressure-sensitive adhesive having good adhesion to a polyolefin by using, as a main component, an emulsion copolymer of ethylene with a satd. carboxylic acid vinyl ester in the pressure of a specific acrylic emulsion. CONSTITUTION:60-99wt.% (meth)acrylic ester monomer with 1-18C alkyl, 0.5-10wt.% unsatd. carboxylic acid selected from the group consisting of (meth) acrylic acid and itaconic acid, and 0-40wt.% copolymerizable monomer are emulsion-copolymerized to give an acrylic emulsion with a glass transition temp. <=-10 deg.C. In the presence of the resulting acrylic emultion, ethylene is copolymerized with a satd. carboxylic acid vinyl ester (e.g., vinyl acetate) to produce an emulsion wherein 20-300 pts.wt. copolymer component of ethylene with the vinyl ester is contained in 100 pts.wt. acrylic resin component. The resulting emulsion is used as a main component of a pressure-sensitive adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention relates to an emulsion-based pressure-sensitive adhesive, and more specifically to an emulsion-based pressure-sensitive adhesive that has excellent adhesive strength to polyolefins such as polyethylene and polypropylene, and has excellent adhesive strength to soft vinyl chloride molded products. The present invention relates to a pressure-sensitive adhesive having adhesive durability.

B. Prior art and problems to be solved by the invention Conventional pressure-sensitive adhesives are made from natural rubber, synthetic rubber, etc. as main raw materials, and are carefully prepared by adding tackifiers, plasticizers, fillers, anti-aging agents, etc. The mainstream was either monomers or solution-type products such as acrylic acid ester copolymers. However, these solution-type pressure-sensitive adhesives use organic solvents and have considerable problems in terms of fire occurrence, occupational health, and pollution such as air pollution. For this reason, in recent years, water-based pressure-sensitive adhesives have attracted attention from the viewpoint of resource saving, non-pollution, and safety and hygiene.
Among these, emulsion-type pressure-sensitive adhesives containing acrylic ester copolymers as a main component are widely used.

Pressure-sensitive adhesives are used in a wide range of applications such as tapes, labels, stickers, and stickers, and the adherend materials include plastic films and molded products, metals, glass, ceramics, paper,
These include cloth and fruits. In particular, the demand for plastic products is increasing, and the proportion of resins such as polyethylene, polypropylene, and polyvinyl chloride has increased significantly due to safety and hygiene considerations. ing.

However, the acrylic emulsion type pressure-sensitive adhesive has drying properties,
Currently, they have drawbacks in water resistance, adhesion, etc., and in particular, adhesion to adherends such as films and molded articles made of polyolefin resins is poor. Methods for improving adhesion to these adherends include softening the pressure-sensitive adhesive and reducing its molecular weight to reduce its cohesive force and improve its adhesion, or adding tackifiers, plasticizers, and There are methods such as blending a water dispersant such as rubber, but all of these methods cause the pressure-sensitive adhesive to protrude from the support due to a decrease in cohesive force, seepage or slits, dirt on the blade during sealing, or a decrease in weather resistance. disadvantages arise.

Another drawback of emulsion-type pressure-sensitive adhesives is that their adhesion to soft vinyl chloride resins deteriorates over time.

In order to improve the drawbacks of such acrylic emulsion type pressure sensitive adhesives, several proposals have been made. One is modification by emulsion blending, in which an acrylic emulsion is blended with an ethylene-vinyl acetate copolymer emulsion (% Publication No. 58-35549, Japanese Patent Publication No. 58-18931), or vinyl acetate-ethylene-vinyl chloride. Sangenkyo i! There is a blend of combined emulsions (JP-A-54-78733). However, in both cases, the glass transition temperature of the modifying polymer is high;
These blends have a practical problem due to decreased adhesion at low temperatures.90Also, acrylic ester-vinyl ester-ethylene ternary copolymers are produced by reacting acrylic esters and vinyl esters in the presence of ethylene. It has also been proposed to use it as a pressure-sensitive adhesive.

(Japanese Patent Publication No. 53-73235, Japanese Patent Application Publication No. 54-61284)
However, these polymers have poor anchoring properties to supports such as paper and films, have low cohesive strength as pressure-sensitive adhesives, and are difficult to perform secondary processing such as slitting, cutting, and punching adhesive tapes or sheets. It has disadvantages such as poor performance.

Seriously, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl chloride copolymer, and ethylene-vinyl acetate-acrylic ester! It has also been proposed that an emulsion obtained by emulsion polymerization of an acrylic ester in the presence of a combined emulsion can be used as a pressure-sensitive adhesive (% 1982-16082). However, although these emulsions have good adhesive durability to soft vinyl chloride resins, they do not have sufficient adhesive strength to polyolefins and have poor low-temperature adhesive properties.

Means for Solving Problem C In view of the above-mentioned circumstances, the present inventors have developed a product that has excellent performance such as adhesion to adherends such as molded products made of polyolefin resin or soft vinyl chloride resin. As a result of intensive studies to obtain an emulsion-type pressure-sensitive adhesive, we found that a specific emulsion obtained by emulsion copolymerization of ethylene and vinyl ester under specific conditions in the presence of a specific acrylic emulsion satisfies the above performance. Heading: How the present invention was accomplished.

That is, the present invention comprises: (260 to 99% by weight of an acrylic ester monomer having an alkyl group having 1 to 18 carbon atoms and/or a methacrylic ester monomer having an alkyl group having 1 to 18 carbon atoms; b) Unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, and itaconic acid: 0.5 to 10 mercury, (c) Other monomers copolymerizable with the above monomers: 0 to 40
Acrylic resin component 100 obtained by emulsion copolymerizing ethylene and saturated carboxylic acid vinyl ester in the presence of an acrylic emulsion having a glass transition temperature of 110° C. or less obtained by total emulsion copolymerization of a monomer mixture consisting of The ratio of ethylene and saturated carboxylic acid vinyl ester copolymer component to parts by weight is 20 to 300! It is a pressure-sensitive adhesive characterized by containing an emulsion as a main component, and has excellent A-order adhesion to molded products made of polyolefin-based fat or soft vinyl chloride resin, and has excellent low-temperature adhesion. It has good properties, and also has good secondary processability such as slitting, cutting, and punching.

The acrylic emulsion in the present invention includes (a) an acrylic ester monomer having an alkyl group having 1 to 18 carbon atoms and/or a methacrylic ester monomer having an alkyl group having 1 to 18 carbon atoms: 60 ~99% by weight, (b) 20.5-10% by weight of an unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, and itaconic acid, (/c) Other monomers copolymerizable with the above monomers: O ~
It is a copolymerization emulsion with a glass transition temperature of 110° C. or less obtained by emulsion copolymerization of a monomer mixture consisting of 40 monomers.

Examples of acrylic esters having 1 to 18 carbon atoms include methyl acrylate, ethyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and decyl acrylate. , lauryl acrylate, and stearyl acrylate. Examples of methacrylic esters having 1 to 18 carbon atoms include methyl methacrylate, ethyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, and -2-methacrylate. Examples include ethylhexyl, dotesyl methacrylate, lauryl methacrylate, and stearyl methacrylate. Particularly preferably, a mixture of an acrylic ester having 4 to 12 carbon atoms and a methacrylic ester having 1 to 4 carbon atoms is used.

If the total monomer content of the acrylic esters and methacrylic esters is less than 60, the adhesive force will not be sufficient as a pressure-sensitive adhesive no matter how the polymerization conditions of ethylene and saturated carboxylic acid vinyl ester are changed. Ta99
If the weight is greater than 1g1S, the cohesive force will be insufficient.

Furthermore, the acrylic emulsion used in the present invention contains an unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, and itaconic acid as an essential component. Adhesion is lost. However, if the weight exceeds 10 weight, not only the water resistance decreases, but also the viscosity decreases.
Preferably, it is necessary to copolymerize 0.8 to 6 of the above-mentioned one or two unsaturated carboxylic acids.

Other monomers that can be copolymerized with these monomers include acrylamide, N-methylolacrylamide, N-methylolacrylamide, and N-methylolacrylamide.
- unsaturated carboxylic acid amides such as butoxymethyl acrylamide and diacetone acrylamide; epoxy group-containing vinyl compounds such as glycidyl acrylate and glycidyl methacrylate; or 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate;
These include hydroxy group-containing monomers such as 2-hydroxyethyl methacrylate, and vinyl monomers such as styrene, acrylonitrile, vinyl acetate, and vinyl chloride.

These monomers can be used to improve the properties of the pressure-sensitive adhesive, such as stabilizing the emulsion, imparting reactivity, and imparting crosslinking properties, without impairing the inherent properties of the pressure-sensitive adhesive.

Further, although the acrylic emulsion in the present invention does not itself need to have basic performance as a pressure-sensitive adhesive, it is necessary that the glass transition temperature of the copolymer be -10°C or lower. At temperatures higher than -10°C, the tackiness is significantly reduced.

The acrylic emulsion of the present invention is obtained by subjecting the monomer mixture to emulsion polymerization in an aqueous medium, if necessary in the presence of an emulsifier, using a radical polymerization initiator.

In the present invention, ethylene and saturated carboxylic acid vinyl ester are emulsion copolymerized in the presence of the above-mentioned specific acrylic emulsion, and the total ratio of ethylene and saturated carboxylic acid vinyl ester copolymer component to xoOit part of the acrylic resin component is By setting the amount to 20 to 300 parts by weight, it can be used for polyolefin resin and soft vinyl chloride resin molded products without impairing adhesion at low temperatures, slitting properties of adhesive labels and tapes, and secondary processability such as punching properties. As a result, an emulsion-type pressure-sensitive adhesive having excellent adhesive properties can be obtained.

If the ethylene-saturated carboxylic acid vinyl ester copolymer component is less than 20ti parts per 100 parts by weight of the acrylic resin component, the adhesive force will be weak and the adhesion to plastics with low polarity will not be sufficiently exhibited. If it exceeds 300 parts by weight, the viscous force is rather impaired and the holding power is also reduced.

In the emulsion copolymerization of ethylene and saturated carboxylic acid vinyl ester of the present invention, it is desirable to employ the following polymerization conditions.

That is, in the presence of an acrylic emulsion, 2
0kf/dG or more, preferably 30ky/cdG to 10
The pressure is increased to 0 kf/-Q, and the polymerization is carried out by continuously or intermittently replenishing the polymerization system so as to maintain the concentration of saturated carboxylic acid vinyl ester monomer in the polymerization system at or below the weight ratio wsit. That's true. Ethylene pressure 20kf/dG
If the concentration of the saturated carboxylic acid vinyl ester monomer exceeds s, tt*, the adhesion to less polar plastics will decrease. The reason for this is to lower the monomer concentration in the polymerization system.
It is thought that a saturated carboxylic acid vinyl ester copolymer is produced, which improves the adhesion to less polar plastics.

The performance of the present invention cannot be obtained by simply blending an acrylic emulsion and an ethylene-saturated carboxylic acid vinyl ester copolymer emulsion. It can only be obtained by emulsion copolymerization under certain conditions.

The saturated carboxylic acid vinyl ester in the present invention is preferably one represented by the general formula % (representing hydrogen or an alkyl group having a total number of carbon atoms of 18 or less), and these include vinyl acetate, vinyl propionate, butyric acid Vinyl, vinyl piperate, vinyl laurate, vinyl versatate, etc. are exemplified, and vinyl acetate or a mixture of vinyl acetate and other vinyl esters are particularly preferred.

The composition of ethylene and saturated vinyl carboxylate ester thus obtained is preferably such that ethylene accounts for 15 to 50% by weight of the total amount of ethylene and saturated vinyl carboxylate ester.

In the emulsion copolymerization of ethylene and saturated carboxylic acid vinyl ester of the present invention, a radical polymerization initiator, a PH adjuster, an emulsifier, and/or a dispersant such as a protective colloid, and a polymerization chain transfer agent are used as necessary.

The radical polymerization initiator used in the present invention is a water-soluble radical initiator used in ordinary emulsion polymerization, such as hydrogen peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, tert-butylhuman peroxide, etc. alone or - Redox systems are used in combination with reducing agents such as ascorbic acid, sulfites, Rongalit, ferrous sulfate.

Suitable dispersants for emulsion polymerization used in the present invention are nonionic surfactants and/or anionic surfactants. Various water-soluble polymers can also be used as protective colloids.

Examples of the nonionic surfactant of the nonionic dispersant used in the present invention include polyoxyethylene lauryl ether, polyoxyethylene octylphenol ether,
Polyoxyethylene alkyl ether and polyoxyethylene alkyl phenol ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan fatty acid ester, ethylene oxide addition amount 10
-aOS polyoxyethylene polyoxypropylene block copolymer and the like are exemplified.

Examples of anionic surfactants used in the present invention include sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium dialkylsulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkylphenol ether sulfate,
Examples include sodium vinyl sulfonate.

In addition, protective colloids include polyvinyl alcohol, partially saponified polyvinyl alcohol, methyl cellulose,
Examples include fiber derivatives such as hydroxyethylcellulose.

As the pHa1 adjuster used in the present invention, acids such as diacid, phosphoric acid, acetic acid, succinic acid, boric acid, carbonic acid, and their salts, alkaline metal hydroxides, ammonia water, amines, etc. are used. be done.

As the chain transfer agent used in the present invention, mercaptan, carbon tetrachloride, chloroform, etc. can be used.

Furthermore, the solid content of the emulsion of the present invention used as a base for pressure-sensitive adhesives must have a high solid content of at least 30% by weight or more, preferably 45% by weight or more. Since it is desirable that the amount of water is small, it is preferable to appropriately adjust the ratio of monomer to water at the stage of producing the emulsion.

The emulsion-type pressure-sensitive adhesive of the present invention having the above structure can be used as is, but if necessary, it may be added with a plasticizer, tackifier, thickener, conditioner, wetting agent, anti-mold agent, etc. It can be added and used. In this case, useful thickeners include celluloses, polyvinyl alcohol, polyacrylates, polymeric surfactants, and alkali thickening acrylic resins.

Supports to which the emulsion-type pressure-sensitive adhesive of the present invention is coated include papers such as fine paper, art paper, coated paper, metallized paper, and kraft paper, polyethylene, polypropylene, polyester, acetate, and polychloride. Examples include films such as vinyl and composites thereof.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these in any way.

In addition, parts and 俤 in the text mean parts by weight and weight %, respectively.

Example 1 In a reactor equipped with a stirrer, 100 parts of water, 20 moles of ethylene oxide, 3 parts of nonylphenol, 0.5 parts of sodium dodecylbenzenesulfonate, and acrylamide (AM
) Add 1 part. Next, 85 parts of 2-ethylhexyl acrylate (2-EHA) and 20 parts of a mixture of 12 parts of methyl methacrylate (MMA) and 2 parts of acrylic acid (AA) were added, and ammonium persulfate was added at 65°C. 90 After the start of polymerization, the remaining 80% of the mixed monomers were added uniformly over 4 hours to obtain an acrylic emulsion (1). The glass transition point (Tg) was determined to be -55°C by DSC.

Next, 100 parts of the resin content of emulsion (1) is transferred to a pressure-resistant autoclave, and 50 parts of a 0.5% concentration hydroxyethyl cellulose aqueous solution and 1 part of nonylphenol added with 20 moles of ethylene oxide are added. Next, 7 parts of vinyl acetate (VAc') was added, the mixture was heated to 50 DEG C. and ethylene pressure was increased to 50 ky/-, and polymerization was initiated using ammonium persulfate and Rongaritol. The concentration of vinyl acetate in the polymerization system was analyzed by iodometric titration by taking appropriate samplings, and 28 parts of vinyl acetate was continuously replenished so that the concentration became 2 to 3%. was held at

The resulting emulsion had a ratio of ethylene-vinyl acetate copolymer to acrylic copolymer of 50:100 according to the solid content concentration and NMR analysis.

The physical properties of the emulsion obtained above as a pressure-sensitive adhesive were evaluated as follows.The emulsion was added with a thickener (Blymar ASE-103, manufactured by Nippon Acrylic Co., Ltd.).
to a viscosity of 15,000 using 25% ammonia water.
Make sure to increase the viscosity to ~20,000 cps (B-type viscometer, 6 rpm). This emulsion type pressure sensitive adhesive is 25 to 30 ? /l (after drying)'? 11 constructions, 110
After drying for 2 minutes at <RTI ID=0.0>C,</RTI> high quality paper (64f#) was laminated to adhesive paper.Physical properties were measured based on JIS-Z-0237. In other words, adhesive strength (adhesive strength)
was measured by the 180 degree peeling method under the conditions of 20℃ and RH65, and the holding force (cohesive force) was determined by the falling time and the bonding area of 25cm.
wX25 electric (vs stainless steel), load 1 Gin, 40℃, RH
The tack was measured under the conditions of 65%, and the tack was measured using the ball propagation method at 20°C and RH 65%. Regarding low-temperature adhesion, the adhesion to various films was evaluated at 0°C by a sensory test. (○ indicates good, Δ indicates slightly poor, and × indicates poor) The obtained results are shown in Table 1.

For adhesion to soft vinyl chloride film, use soft vinyl chloride film A (DOP) instead of the above adhesive paper with stainless steel.
30phr product) and measured the adhesive strength (adhesive strength) immediately after lamination at 20°C and after 14 days using the 180 degree peeling method.

Example 2 100 parts of the resin content of the acrylic emulsion (1) obtained in Example 1 was added to a pressure-resistant autoclave, and 100 parts of an aqueous solution of polyvinyl alcohol of 20% and 3% of ethylene oxide were added.
Add 2 parts of 0 mole added nonylphenol. Next, 5 parts of vinyl acetate and 5 parts of Veova-10 (trade name of Shell) were added, and the mixture was heated at 60°C under an ethylene pressure of 50 k.
Pressurize to f/cti and start polymerization using hydrogen peroxide solution and Rongalite. Next, 30 parts of vinyl acetate and Veo
va-10030 parts of the mixture was continuously added to the polymerization system so that the concentration of these vinyl esters was 40%, and the polymerization was proceeded to obtain t0. The resulting t emulsion was determined by NMR analysis to be a mixture of ethylene-vinyl ester copolymer and acrylic copolymer. The combination ratio is 100:100.

This emulsion was evaluated as a pressure-sensitive adhesive in the same manner as in Example 1. The results are shown in Table 1.0 Example 3 The resin content of the acrylic emulsion obtained in Example 1 was 10.
Polymerization was carried out in the same manner as in Example 1, except that the vinyl acetate monomer concentration during polymerization in Example 10 was maintained at 2 to 3% at a total of 10 parts, to obtain emulsion/.

The ratio of ethylene-vinyl acetate copolymer to acrylic copolymer in the obtained emulsion was determined by NMR to be 41:100.
Met. The performance evaluation results of the obtained emulsion were evaluated first.
Shown in the table.

Comparative Example 1 After adding 100 parts of water, 20 moles of ethylene oxide, 3 parts of nonylphenol, 0.5 part of sodium dodecylbenzenesulfonate, and 1 part of acrylamide to a reactor, 80 parts of ethyl acrylate (EA), 17 parts of MMA, AA
Polymerization was carried out in the same manner as in Example 1 using the mixed monomers in the Z part, resulting in an acrylic emulsion (If) with a Tg of 15°C.
! friend.

Next, emulsion copolymerization of ethylene and vinyl acetate was carried out in the same manner as in Example 1 in the presence of 100 parts of the above acrylic emulsion resin. The performance evaluation results of the obtained emulsion are shown in Table 1. Comparative Example 2 In the presence of 100 parts of the resin content of the acrylic emulsion (1) obtained in Example 1, 350 parts of a 0.5* hydroxy engineered cellulose aqueous solution and Add 20 moles of ethylene oxide and 7 parts of nonylphenol. Then 25 parts of vinyl acetate were added and the ethylene pressure was increased to 50 Bcf at 50°C.
/all, and start polymerization using ammonium persulfate and Rongalite.

Next, 203 parts of vinyl acetate was continuously added so that the concentration of vinyl acetate in the polymerization system was 2 to 3, and the polymerization was proceeded.

The resulting emulsion had a ratio of ethylene-vinyl acetate copolymer to acrylic copolymer of 350:100. Table 1 shows the performance evaluation results of this emulsion.

Comparative Example 3 100 parts of a 0.5% hydroxyethyl cellulose aqueous solution and 2 parts of nonylphenol added with 20 moles of ethylene oxide were added to a pressure-resistant autoclave for 7 tons.

Next, t-10 parts of vinyl acetate was added, the ethylene pressure was increased to 50 kl/cd at 50°C, and polymerization was started using ammonium persulfate and a-garite. Next, 52 parts of vinyl acetate was continuously added so that the concentration of vinyl acetate in the polymerization system was 2 to 3% to advance the polymerization, resulting in an ethylene-vinyl acetate copolymer emulsion (EVA emulsion (1)).
) The ethylene content of the emulsion was determined to be 38% by weight by NMR.

Next, the acrylic emulsion obtained in Example 1 was mixed with the EVA emulsion (resin content: 100:25).
The performance of the adhesive as a pressure-sensitive adhesive was evaluated. The results are shown in Table 1. As is clear from Table 1, Examples 1, 2 and 3 of the present invention have a well-balanced adhesive property (tack, holding power, beer), and are particularly effective against polyolefin resins. It has excellent adhesive strength and also has good adhesion at low temperatures. On the other hand, Comparative Examples 1 to 3, which are outside the scope of the present invention, have low adhesion to polyolefins and lack a balance in the three adhesion properties.

For reference, in Example 1, Tokuji acrylic emulsion (
1) Performance evaluation results for individual pressure-sensitive adhesives are shown in Table 1 as a reference example.

Claims (3)

[Claims] (1) (A) Acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms and/or methacrylic ester monomer having an alkyl group having 1 to 18 carbon atoms: 60 to
99% by weight, (b) Unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, and itaconic acid: 0.5 to 10% by weight, (c) Other monomers copolymerizable with the above monomers: 0 ~40
An acrylic resin component obtained by emulsion copolymerizing ethylene and a saturated carboxylic acid vinyl ester in the presence of an acrylic emulsion having a glass transition temperature of -10°C or less obtained by emulsion copolymerizing a monomer mixture consisting of A pressure-sensitive adhesive characterized in that its main component is an emulsion in which the ratio of ethylene and saturated carboxylic acid vinyl ester copolymer components to 100 parts by weight is 20 to 300 parts by weight. (2) In emulsion copolymerization of ethylene and saturated carboxylic acid vinyl ester, polymerization is carried out under an ethylene pressure of 20 kg/cm^2G or more, while maintaining the concentration of saturated carboxylic acid vinyl ester in the polymerization system at 5% by weight or less. Claim (1) wherein the polymerization is carried out by continuously or intermittently replenishing the system.
) Pressure sensitive adhesives described in ). (3) The pressure-sensitive adhesive according to claim (1), wherein the saturated carboxylic acid vinyl ester is a vinyl ester represented by the following formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R_1, R_2, R_3 represent hydrogen or an alkyl group with a total number of carbon atoms of 18 or less.)