JP2642149B2 - Pressure sensitive adhesive - Google Patents

Description

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

B. Problems to be Solved by the Prior Art and the Invention Conventional pressure-sensitive adhesives are mainly made of natural rubber, synthetic rubber, and the like, to which a tackifier, a plasticizer, a filler, an antioxidant, and the like are added. Or a solution type such as an acrylate-based copolymer was the mainstream. However, since these solution-type pressure-sensitive adhesives use an organic solvent, they have various problems in terms of pollution such as fire, occupational health, and air pollution. Therefore, in recent years, water-based pressure-sensitive adhesives have attracted attention from the viewpoint of resource saving, pollution-free, and safety and health, and among them, emulsion type pressure-sensitive adhesives containing an acrylate copolymer as a main component have been widely used. ing.

The applications of pressure-sensitive adhesives cover a wide range such as tapes, labels, stickers and seals, and the adherends are made of plastic films and molded products, metallic glass, ceramics, paper,
Cloths and fruits. In particular, the demand for plastic products has increased, and the proportion of resins such as polyethylene, polypropylene, and polyvinyl chloride has increased significantly in terms of safety and hygiene. ing.

However, the acrylic emulsion-type pressure-sensitive adhesive has drawbacks in dryness, water resistance, adhesiveness, and the like, as compared with conventional solution-type pressure-sensitive adhesives.
In particular, at present, adhesion to adherends such as films and molded articles made of polyolefin resin is poor. As a method of improving the adhesion to these adherends, a method of softening or reducing the molecular weight of the pressure-sensitive adhesive to lower the cohesive force to improve the adhesion, or a tackifier, a plasticizer, a rubber, and the like. There is a method of blending the water dispersant of the above, but in any case, the pressure-sensitive adhesive protrudes from the support due to a decrease in cohesion, penetrates or slits, stains on the blade at the time of sealing, or defects such as a decrease in weather resistance Occurs.

Another disadvantage of the acrylic emulsion type pressure-sensitive adhesive is that the adhesion to a soft vinyl chloride resin decreases with time.

A few proposals have been made to improve such disadvantages of the acrylic emulsion type pressure-sensitive adhesive. One is modification by an emulsion blend, which is a blend of an acrylic emulsion and an ethylene-vinyl acetate copolymer emulsion (JP-B-58-3559, JP-B-58).
18931), or a blend of vinyl acetate-ethylene-vinyl chloride terpolymer emulsion (JP-A-54-78738). However, in any case, since the glass transition point of the modifying polymer is high, the adhesion of these blends at low temperature is lowered, and there is a problem in practical use.

It has also been proposed to use an acrylate-vinyl ester-ethylene terpolymer obtained by reacting an acrylate and a vinyl ester in the presence of ethylene as a pressure-sensitive adhesive. However, these polymers have poor anchoring properties to substrates such as paper and film, have low cohesive strength as a pressure-sensitive adhesive, and furthermore have poor adhesion. It has disadvantages such as poor secondary workability such as slitting, cutting, and punching of the tape or sheet.

Further, in the presence of an emulsion of an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-vinyl chloride copolymer or an ethylene-vinyl acetate-acrylate copolymer, an emulsion obtained by emulsion polymerization of an acrylate ester is sensed. It has also been proposed to use as a pressure-sensitive adhesive (JP-A-57-16082). However, these emulsions have good adhesion durability to a soft vinyl chloride resin, but have insufficient adhesion to polyolefin and low-temperature adhesion.

C. Means for Solving the Problems In view of such circumstances, the present inventors have developed excellent performance such as adhesiveness for adherends such as molded articles made of polyolefin resin or soft vinyl chloride resin. As a result of intensive studies to obtain an emulsion type pressure-sensitive adhesive having, it was found that, in the presence of a specific acrylic emulsion, a specific emulsion obtained by emulsion copolymerization of ethylene and vinyl ester under specific conditions satisfies the above performance. This led to the completion of the present invention.

That is, the present invention provides (a) an acrylate 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 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 monomer copolymerizable with the above monomer: 0 to 40% by weight In the presence of an acrylic emulsion having a glass transition temperature of −10 ° C. or less under emulsion pressure of 20 kg / cm ² G or more of ethylene, a saturated carboxylic acid vinyl ester in the polymerization system is obtained. 100 parts by weight of an acrylic resin component obtained by continuously or intermittently replenishing a saturated vinyl carboxylate to the polymerization system so as to maintain the concentration at 5% by weight or less and emulsion-copolymerizing ethylene and the saturated vinyl carboxylate. Part Is a pressure-sensitive adhesive characterized in that the main component is an emulsion in which the proportion of ethylene and a saturated carboxylic acid vinyl ester copolymer component is 20 to 300 parts by weight, comprising a polyolefin resin or a soft vinyl chloride resin It has excellent adhesiveness to molded products, good low-temperature adhesiveness, and good secondary workability such as slitting, cutting, and punching.

The acrylic emulsion in the present invention comprises: (a) an acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms and / or a methacrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms: 60 to 99 (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 to 40% by weight % Is obtained by emulsion copolymerization of a monomer mixture consisting of% by weight and a glass transition temperature of -10 ° C. or lower.

Examples of the acrylate having 1 to 18 carbon atoms include methyl acrylate, ethyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate , Lauryl acrylate, and stearyl acrylate. Examples of the methacrylate having 1 to 18 carbon atoms include methyl methacrylate, ethyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, and 2-ethylhexyl methacrylate. , Dodecyl methacrylate, lauryl methacrylate, stearyl methacrylate and the like, and particularly preferably an acrylate having 4 to 12 carbon atoms and 1 to 1 carbon atoms.
A mixture of 4 methacrylates is used.

If the total amount of the acrylate and / or methacrylate monomers is less than 60% by weight, the adhesive force is not sufficient as a pressure-sensitive adhesive even if the polymerization conditions of ethylene and the saturated carboxylic acid vinyl ester are changed, and 99% by weight. If it is larger, the cohesive strength is insufficient.

Further, in the acrylic emulsion used in the present invention, an unsaturated carboxylic acid selected from acrylic acid, methacrylic acid, and itaconic acid is an essential component. If the unsaturated carboxylic acid is less than 0. 0% by weight, the adhesive strength to plastic is obtained. Is lost. However, if it exceeds 10% by weight, not only the water resistance is reduced but also the tackiness is reduced, and 0.5 to 10% by weight, preferably 0.8 to 6% by weight of the above one or two unsaturated carboxylic acids are copolymerized. There is a need.

Other monomers copolymerizable with these monomers include acrylamide, N-methylolacrylamide,
Unsaturated carboxylic acid amides such as N-butoxymethyl acrylamide and diacetone acrylamide, epoxy group-containing vinyl monomers such as glycidyl acrylate and glycidyl methacrylate, or 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and 2-hydroxy Hydroxy group-containing monomers such as ethyl methacrylate; and vinyl monomers such as styrene, acrylonitrile, vinyl acetate, and vinyl chloride.

These monomers can be used for improving the stability of the emulsion, imparting the reactivity, imparting the cross-linking property, etc. without impairing the original properties as a pressure-sensitive adhesive.

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

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

In the present invention, in the presence of the above-mentioned specific acrylic emulsion, ethylene and a saturated vinyl carboxylate are emulsion-copolymerized under specific conditions and an acrylic resin component is formed.
By adjusting the ratio of the ethylene and saturated carboxylic acid vinyl ester copolymer component to 100 parts by weight to 20 to 300 parts by weight, secondary processing properties such as adhesiveness at low temperature, slitting properties of adhesive labels and tapes and punching properties, etc. An emulsion-type pressure-sensitive adhesive having excellent adhesiveness to a polyolefin-based resin and a soft vinyl chloride resin molded product can be obtained without impairing the composition.

If the ethylene-saturated carboxylic acid vinyl ester copolymer component is less than 20 parts by weight with respect to 100 parts by weight of the acrylic resin component, the adhesive strength is weak, and the adhesiveness to a small-polarity plastic is not sufficiently exhibited, and If it exceeds 300 parts by weight, the adhesive strength will be impaired, and the holding power will also decrease.

In the emulsion copolymer of ethylene and a saturated carboxylic acid vinyl ester of the present invention, it is necessary to adopt the following polymerization conditions.

That is, ethylene is present in the presence of an acrylic emulsion.
20 kg / cm ² G or more, preferably to maintain a pressure of ^{30kg / cm 2 G~100kg / cm 2} G pressurize the concentration of saturated carboxylic acid vinyl ester monomer in the polymerization system to 5 wt% or less To conduct polymerization by continuously or intermittently replenishing the polymerization system. If the ethylene pressure is less than 20 kg / cm ² G, or if the concentration of the saturated vinyl carboxylate monomer exceeds 5% by weight, the adhesion to plastics having low polarity is reduced.
The reason for this is considered that a low molecular weight ethylene-saturated carboxylic acid vinyl ester copolymer is produced by lowering the monomer concentration of the polymerization system, and this is thought to improve the adhesiveness to plastics having a small polarity. Can be

The performance of the present invention is based on acrylic emulsion and ethylene-
It is difficult to obtain by simple blending with a saturated carboxylic acid vinyl ester copolymer emulsion, but only by emulsion copolymerization of ethylene and a saturated carboxylic acid vinyl ester under specific conditions in the presence of a specific acrylic emulsion. It is.

The saturated carboxylic acid vinyl ester in the present invention has a general formula (However, R ₁ , R ₂ , and R ₃ are preferably hydrogen or an alkyl group having a total of 18 or less carbon atoms), such as vinyl acetate, vinyl propionate, vinyl butyrate, and pivalin. Examples thereof include vinyl acid, vinyl laurate, and vinyl versatate, and particularly preferably vinyl acetate or a mixture of vinyl acetate and another vinyl ester.

The composition of ethylene and saturated vinyl carboxylate thus obtained is desirably 15 to 50% by weight of ethylene based on the total amount of ethylene and saturated vinyl carboxylate.

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

The radical polymerization initiator in the present invention is a water-soluble radical initiator used for ordinary emulsion polymerization, for example, hydrogen peroxide, potassium persulfate, sodium persulfate, ansenium persulfate, tert-butyl hydroperoxide or the like alone or A redox system in combination with a reducing agent such as L-ascorbic acid, sulfite, Rongalite, ferrous sulfate is used.

Suitable as a dispersant for the emulsion polymerization used in the present invention are nonionic surfactants and / or anionic surfactants. In addition, various water-soluble polymers can be used as the protective colloid.

Examples of the nonionic surfactant of the nonionic dispersant used in the present invention include polyoxyethylene lauryl ether, polyoxyethylene octyl phenol ether, polyoxyethylene nonyl phenol ether, polyoxyethylene alkyl ether such as polyoxyethylene alkyl ether and polyoxyethylene nonyl surfactant. Ethylene alkylphenol ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan fatty acid ester, ethylene oxide addition amount
Examples include 10-80% polyoxyethylene polyoxypropylene block copolymer.

Examples of the anionic surfactant used in the present invention include sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium dialkylsulfosuccinate, sodium polyoxyethylene alkyl etherate, sodium polyoxyethylene alkylphenol ether sulfate,
Sodium vinyl sulfonate is exemplified.

Examples of the protective colloid include fibrous derivatives such as polyvinyl alcohol, partially saponified polyvinyl alcohol, methyl cellulose, and hydroxyethyl cellulose.

As the PH regulator used in the present invention, hydrochloric acid,
Acids such as phosphoric acid, acetic acid, succinic acid, boric acid, and carbonic acid and salts thereof, alkali metal hydroxides, aqueous ammonia, and bases such as amines are used.

As the chain transfer agent used in the present invention, mercaptan,
Carbon tetrachloride, chloroform and the like can be used. Further, the solid content of the emulsion of the present invention used as a base of the pressure-sensitive adhesive is a high solid content of at least 30% by weight or more, preferably 45% by weight or more. Since it is desirable to reduce the size of the emulsion, it is preferable to adjust the ratio of the monomer and water appropriately in the step of producing the emulsion.

The emulsion type pressure-sensitive adhesive having the above structure of the present invention is:
Although it can be used as it is, if necessary, it can be used by adding a desensitizing agent, a tackifier, a thickener, a PH adjuster, a wetting agent, a fungicide and the like. In this case, as the thickener, celluloses, polyvinyl alcohol, polyacrylates, polymer surfactants, alkali thickening acrylic resins, and the like are useful.

Examples of the support on which the emulsion type pressure-sensitive adhesive of the present invention is applied include papers such as high-quality paper, art paper, coated paper, metallized paper and kraft paper, polyethylene, polypropylene, polyester, acetate and polychlorinated paper. Examples thereof include films of vinyl and the like and composites thereof.

Next, the present invention will be described with reference to examples, but the present invention is not limited thereto. Parts and% in the text mean parts by weight and% by weight, respectively.

Example 1 A reactor equipped with a stirrer was charged with 100 parts of water and ethylene oxide 2
3 parts of 0 mole addition nonylphenol, 0.5 part of sodium dodecylbenzenesulfonate and 1 part of acrylamide (AM) are added. Then 85 parts of 2-ethylhexyl acrylate (2-EHA) and methyl methacrylate (MMA)
20% of the total amount of the mixture of 12 parts and 2 parts of acrylic acid (AA)
And polymerized at 65 ° C. using ammonium persulfate. Over 4 hours after the start of the polymerization, the remaining 80% of the mixed monomer was uniformly added to obtain an acrylic emulsion (I). The glass transition point (Tg) was -55 ° C by DSC.

Next, 100 parts of the resin component of the emulsion (I) is transferred to a pressure-resistant autoclave, and 50 parts of a 0.5% aqueous solution of hydroxyethylcellulose and 1 part of nonylphenol added with 20 mol of ethylene oxide are added. Then, 7 parts of vinyl acetate (VAc) was added, the pressure was increased to 50 kg / cm ² at 50 ° C., and polymerization was started using ammonium persulfate and Rongalite. Sampling is performed as appropriate, and the concentration of the vinyl acetate in the polymerization system is analyzed by iodine titration.
28 parts of vinyl acetate was continuously supplied so that the concentration became 3%, and the polymerization was advanced. During this time, the ethylene pressure was kept constant.

From the solid content concentration and NMR analysis, the obtained emulsion had a ratio of ethylene-vinyl acetate copolymer to acrylic copolymer of 50: 100.

The evaluation of the physical properties of the emulsion thus obtained as a pressure-sensitive adhesive was carried out as follows.

A thickener (Nippon Acrylic Co., Brimar ASE-108) is added to the emulsion and the viscosity is adjusted using 25% aqueous ammonia.
The viscosity increased to 15,000 to 20,000 cps (B-type viscometer, 6 rpm).
25~30g The Emarujiyon type pressure sensitive adhesive release paper / m ²
(After drying) Coated and dried at 110 ° C for 2 minutes, then fine wood (64g
/ m ² ) to obtain adhesive paper.

Physical properties of this adhesive paper were measured based on JIS-Z-0237. That is, the adhesive force (adhesive force) is measured by a 180-degree peeling method under the conditions of 20 ° C. and 65% RH. The measurement was carried out at 40 ° C. and 65% RH, and the tack (adhesion) was measured by the ball rolling method at 20 ° C. and 65% RH.
Regarding the low-temperature adhesiveness, the adhesiveness to various films at 0 ° C. was evaluated by a sensory test. (○ is good, △
Table 1 shows the obtained results.

For the adhesion to flexible vinyl chloride film, replace the above-mentioned adhesive paper with stainless steel and use a flexible vinyl chloride film (DOP30p
hr product), and immediately after lamination at 20 ° C. and 14 days later, the adhesive strength (adhesive strength) was measured by a 180 ° peeling method.

Example 2 Acrylic emulsion (I) tree obtained in Example 1
Add 100 parts of fat to autoclave and add 2%
100 parts of vinyl alcohol aqueous solution and 30 parts of ethylene oxide
2 parts of nonylphenol are added. Next,
Nyl 5 parts and Veova-10 (Ciel's product name) with 5 parts
And ethylene pressure 50kg / cm at 60 ℃^TwoPressure and peroxidation
Polymerization was started using hydrogen water and Rongalite. Then
30 parts of vinyl acetate and Veova-10 30 parts of the mixture are polymerized
Continuous so that the concentration of these vinyl esters is 4%
To proceed with polymerization.

The resulting emulsion was analyzed by NMR to have a ratio of ethylene-vinyl ester copolymer and acrylic copolymer of 100: 100.
It was.

This emulsion was evaluated as a pressure-sensitive adhesive in the same manner as in Example 1. The results are shown in Table 1.

Reference Example 1 The resin content of the acrylic emulsion obtained in Example 1 was 10
Using 0 part, polymerization was carried out in the same manner as in Example 1 except that the vinyl acetate monomer concentration during the polymerization in Example 1 was kept at 10% instead of keeping it at 2 to 3%, and an emulsion was obtained.

The ratio of the ethylene-vinyl acetate-copolymer to the acrylic copolymer of the obtained emulsion was 41: 100 by NMR. Table 1 shows the performance evaluation results of the obtained emulsion.

Comparative Example 1 100 parts of water, 3 parts of nonylphenol added with 20 moles of ethylene oxide, 0.5 part of sodium dodecylbenzenesulfonate and 1 part of acrylamide were added to a reactor, and then a mixed monomer of 80 parts of ethyl acrylate (EA), 17 parts of MMA, and 2 parts of AA was added. Was used to carry out polymerization in the same manner as in Example 1 to obtain an acrylic emulsion (II) having a Tg of -5 ° C.

Then, 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-mentioned acrylic emulsion resin. Table 1 shows the performance evaluation results of the obtained emulsion.

Comparative Example 2 In the presence of 100 parts of the resin component of the acrylic emulsion (I) obtained in Example 1, 350 parts of a 0.5% aqueous solution of hydroxyethylcellulose and 7 parts of nonylphenol added with 20 mol of ethylene oxide are added. Next, 25 parts of vinyl acetate was added, the pressure was increased to 50 kg / cm ² at 50 ° C., and polymerization was started using ammonium persulfate and Rongalite.
Next, 203 parts of vinyl acetate was continuously added so that the concentration of the vinyl acetate in the polymerization system became 2 to 3%, and the polymerization was advanced.

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 To a pressure-resistant autoclave, 100 parts of a 0.5% aqueous solution of hydroxyethylcellulose and 2 parts of nonylphenol added with 20 mol of ethylene oxide were added. Then add vinyl acetate for 10
Parts was added, pressurized to ethylene pressure 50 kg / cm ² at 50 ° C., the polymerization was initiated using ammonium persulfate and Rongaritsuto. Next, 52 parts of vinyl acetate was continuously added so that the concentration of the vinyl acetate in the polymerization system became 2 to 3%, and the polymerization was advanced.
An ethylene-vinyl acetate copolymer emulsion (EVA emulsion (I)) was obtained. The ethylene content of the emulsion was 38% by weight by NMR.

Next, the acrylic emulsion (I) obtained in Example 1 and the EVA emulsion (I) were mixed in a resin content of 100: 25.
And the performance 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 good balance of three adhesive properties (tack, holding power, and beer), and particularly have excellent adhesive strength to polyolefin resin. Further, the adhesiveness at low temperatures is also good. On the other hand, those of Comparative Examples 1 to 3, which deviate from the present invention, have low adhesive strength to polyolefin and lack the balance of the three physical properties of adhesive.

Reference Example 2 For reference, the performance evaluation results of the acrylic emulsion (I) alone obtained in Example 1 as a pressure-sensitive adhesive are shown in Table 1 as Reference Examples.

Continuation of the front page (72) Inventor Junnosuke Yamauchi 1621 Sazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. Examiner Yumiko Isshiki

Claims (2)

(57) [Claims] 1. An acrylic acid ester monomer having an alkyl group having 1 to 18 carbon atoms and / or 1 to 18 carbon atoms.
Methacrylic acid ester monomer having an alkyl group of: 60
(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 to In the presence of an acrylic emulsion having a glass transition temperature of −10 ° C. or less, obtained by emulsion copolymerization of a monomer mixture consisting of 40% by weight, under the pressure of ethylene of 20 kg / cm ² G or more, the saturated carboxylic acid in the polymerization system is Acrylic resin obtained by copolymerizing ethylene and a saturated carboxylic acid vinyl ester by continuously or intermittently replenishing the polymerization system with a saturated carboxylic acid vinyl ester so as to maintain the concentration of the acid vinyl ester at 5% by weight or less. A pressure-sensitive adhesive characterized in that it contains, as a main component, an emulsion containing 20 to 300 parts by weight of ethylene and a saturated carboxylic acid vinyl ester copolymer component per 100 parts by weight of the component. 2. The pressure-sensitive adhesive according to claim 1, wherein the saturated carboxylic acid vinyl ester is a vinyl ester represented by the following formula. (However, R ₁ , R ₂ , and R ₃ represent hydrogen or an alkyl group having a total of 18 or less carbon atoms.)