JPH0145505B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pressure-sensitive adhesive for polyvinyl chloride molded products, and more particularly to a copolymer having a multilayer structure in which the (most) inner layer and (most) outer layer are each composed of a specific (co)polymer. Adhesive-treated tapes, sheets, etc. whose main ingredient is coalescent emulsion.
When bonding a support such as a panel to an adherend,
At least one of these supports and adherends is a polyvinyl chloride compound (hereinafter referred to as plasticizer) containing a so-called low molecular weight plasticizer such as dioctyl phthalate (DOP), dibutyl phthalate (DBP) or diisobutyl phthalate (DIBP). It can be applied to the adhesion of polyvinyl chloride molded products such as polyvinyl chloride (abbreviated as polyvinyl chloride), and has an emulsion-type feel that maintains excellent adhesive strength even after a long period of time after it has been adhered and pasted. Regarding pressure adhesives. In recent years, as a movement toward resource conservation and pollution-free production,
In the field of this type of pressure-sensitive adhesive, there is also a growing demand for solvent-free adhesives, and organic solvent-based pressure-sensitive adhesives, which had traditionally dominated the market, are gradually being replaced by water-based emulsion adhesives. It is being done. By the way, in the field of tapes and sheets that use molded products made from plasticized polyvinyl chloride as supports and adherends, the low molecular weight plasticizer contained in such polyvinyl chloride is added to adhesive compositions over time. However, conventional emulsion-type pressure-sensitive adhesives have not been able to adequately address this problem, such as the continued decline in adhesive properties, especially cohesive strength. The current situation is that it cannot be achieved. On the other hand, some emulsion-type pressure-sensitive adhesives that are crosslinked using reactive polar groups have been available in the past in order to solve the above-mentioned problems. Although some adhesives have been shown to have some effect on the migration of low-molecular-weight plasticizers over time, their adhesive strength at low temperatures is markedly reduced and their adhesion to the support is poor. It can be said that it is extremely difficult to maintain and maintain a high level of adhesive force and cohesive force in a well-balanced manner. In view of these circumstances, the purpose of the present invention is to first provide excellent adhesive strength even in a wide temperature range, which was not possible with the conventional emulsion type pressure-sensitive adhesives mentioned above, and in addition, to provide low adhesive strength from polyvinyl chloride molded products. It is an object of the present invention to provide a new and useful emulsion-type pressure-sensitive adhesive that can also suppress migration of molecular weight plasticizer as much as possible. The inventors of the present invention have made extensive studies with the above objectives in mind, and have found that the above-mentioned problems have been successfully solved by the combination of the particle structure and crosslinked structure of the copolymer emulsion, which is the main ingredient of the pressure-sensitive adhesive. By discovering a useful emulsion-type pressure-sensitive adhesive, the present invention has been completed. That is, in the present invention, the dispersed particles constituting the copolymer emulsion as the main ingredient have a multilayer structure consisting of at least two layers, and the copolymer (A ₁ ) forming the (innermost) layer is made of epoxy. 0.1 to 10 parts by weight of an α,β-ethylenically unsaturated monomer (a-1) having a group, and an α,β-ethylenically unsaturated monomer having a polar group reactive with this epoxy group. 0.1 to 20 parts by weight of the body (a-2),
Obtained from 99.8 to 70 parts by weight of each of these monomers (a-1) and (a-2) and other copolymerizable α,β-ethylenically unsaturated monomer (a-3). and the copolymer (A ₂ ) forming the (most) outer layer is a 60 to 100 alkyl acrylate and/or alkyl methacrylate (a- ₄ ) having an alkyl group of C4 or more. weight part,
It is obtained from this and 40 to 0 parts by weight of another copolymerizable α,β-ethylenically unsaturated monomer (a-3), and the Tg of the copolymer (A ₁ ) is -
The present invention provides a pressure-sensitive adhesive for polyvinyl chloride molded products, which contains a multilayer structure copolymer as a main ingredient, and which has a temperature of 40°C to +20°C. Here, the above-mentioned epoxy group-containing α, β
- Representative examples of the ethylenically unsaturated monomer (a-1) include (β-methyl)glycidyl methacrylate, (β-methyl)glycidyl methacrylate, or allyl glycidyl ether,
In addition, typical examples of the above-described α,β-ethylenically unsaturated monomer (a-2) having a reactive polar group include acrylic acid, methacrylic acid, crotonic acid,
Unsaturated monobasic acids or their salts such as vinylsulfonic acid or vinyltoluenesulfonic acid; unsaturated dibasic acids or their half esters such as itaconic acid, maleic acid or fumaric acid; vinyltriethoxysilane or vinyltris Vinylsilanes such as (β-methoxyethoxy)silane; vinylamides such as acrylamide, methacrylamide, diacetone acrylamide or N-methylolacrylamide;
Hydroxyl group-containing vinyl monomers such as β-hydroxyacrylate or β-hydroxymethacrylate; or amino group-containing vinyl monomers such as alkylaminoacrylate or alkylaminomethacrylate. On the other hand, typical (meth)acrylic esters (a-4) having a C ₄ alkyl group used to prepare the polymer (A ₂ ) include n-butyl, i-butyl or t-Butyl (meth)acrylate, n-amyl (meth)acrylate, hexyl (meth)acrylate, 2-
Examples include ethylhexyl, (meth)acrylate, octyl (meth)acrylate or nonyl (meth)acrylate. In addition, other radically copolymerizable α,β-ethylenically unsaturated monomers (a-3) used to prepare the above-mentioned copolymers (A ₁ ) and (A ₂ ) are also represented. Examples include vinyl acetate, vinyl propionate, vinyl versatate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, styrene, (meth)acrylonitrile, ethylene, propylene, butadiene or isoprene. be. In addition, in preparing the copolymer (A ₂ ), if necessary, an epoxy group-containing α,β-ethylenic material as used in preparing the copolymer (A ₁ ) may be used. There is nothing that precludes the use of a part of the unsaturated monomer (a-1) or the reactive polar group-containing α,β-ethylenically unsaturated monomer (a-2). When obtaining the copolymer emulsion which is the main ingredient of the adhesive of the present invention, the ratio of the above-mentioned copolymer (A ₁ ) and copolymer (A ₂ ) is 5:5 by weight.
It is appropriate to keep it within the range of 95 to 50:50,
In addition, from the viewpoint of the tackiness, cohesive force, and adhesion at low temperatures of the multilayer copolymer emulsion as the main ingredient, the Tg (glass transition point) of the copolymer (A ₁ ) is -40°C to It is preferable that the temperature is within the range of +20℃, and the weight average molecular weight () in terms of polystyrene as measured by gel permeation chromatography (GPC) of the copolymer (A ₁ ) is 5×10 ³ ~
A suitable number is 5×10 ⁵ , preferably 1×10 ⁴ to 2×10 ⁵ . In addition, when preparing the copolymer emulsion, it is possible to prepare the copolymer emulsion without using any emulsifier, or by using a known and commonly used emulsion as shown below, and an emulsion dispersion such as a water-soluble oligomer or polymer. It can also be achieved by using it in combination with agents. Typical emulsifiers include anionic surfactants such as aralkyl sulfonates such as sodium dodecylbenzenesulfonate or sulfates of alkaryl polyether; polyoxyethylene nonyl phenyl ether or polyoxyethylene- Examples include nonionic surfactants such as polyoxypropylene block copolymers; or cationic surfactants such as laurylpyridium chloride or cetyltrimethylammonium bromide. Furthermore, typical polymerization initiators used in preparing the copolymer emulsion include known and commonly used initiators such as hydrogen peroxide, ammonium persulfate, potassium persulfate, and t-butyl hydroperoxide. Furthermore, it may be used in the form of a redox initiator, which is a combination of such a polymerization initiator and a reducing substance such as ascorbic acid or sulfites. The multilayer copolymer emulsion, which is the main ingredient of the adhesive of the present invention, can be prepared by a known and commonly used emulsion polymerization method using the various raw materials listed above.
A range of 90℃ is appropriate, and the solid content of the final multilayer copolymer emulsion is 30 to 65% by weight.
It is preferable that the emulsifier or emulsifier/dispersant is used only in the step of _preparing the copolymer (A ₁ ), and the amount of the emulsifying agent or emulsifying dispersant used should be ) and copolymer (A ₂ ), preferably 0.2 to 10% based on the total weight of
A range of 0.5 to 5% is appropriate, but in some cases, at the stage of preparing the copolymer (A ₂ ),
Alternatively, it can be added again during multi-stage (co)polymerization by repeating each radical (co)polymerization reaction to obtain both copolymers (A ₁ ) and (A ₂ ). The thus obtained copolymer emulsion having a multilayer structure of two or more layers can be applied as it is to various molded products of plasticized polyvinyl chloride, as well as supports such as paper or cloth. The combined emulsion is the main ingredient, and if necessary, known and commonly used tackifiers, tackifiers, stabilizers, thickeners, pigments, fillers, wetting agents, antifoaming agents, etc. may be added as appropriate. Regardless of how it is used, as long as the adhesive of the present invention is used, it has excellent adhesion to supports and/or adherends, including polyvinyl chloride molded products, and has low cohesive strength due to the transfer of plasticizer. A pressure-sensitive adhesive with no decrease in temperature can be obtained. Next, the present invention will be specifically explained using reference examples, examples, and comparative examples, and all parts and percentages are based on weight unless otherwise specified. Reference Example 1 (Preparation example of two-layer copolymer emulsion) 100 parts of deionized water and "Neogen R" [Daiichi Kogyo Seiyaku Co., Ltd.] were placed in a reaction vessel equipped with a stirrer, a condenser, a thermometer, and a dropping funnel. Emulsifier] No. 2
After stirring and keeping the internal temperature at 80°C, and introducing nitrogen gas into the container, a mixture consisting of 12 parts of ethyl acrylate, 5 parts of vinyl acetate, 1 part of glycidyl methacrylate, and 1 part of methacrylic acid was prepared. and a mixture consisting of 0.25 parts of potassium persulfate and 5 parts of deionized water were injected separately over a period of about 1 hour, and the reaction was continued by holding at temperature for an additional hour to complete the first stage. The polymerization reaction was completed.
What was obtained here is a copolymer that becomes the so-called inner layer. Hereinafter, this will be abbreviated as copolymer (A ₁ -1). Thereafter, at the same temperature, a mixture of 80 parts of n-butyl acrylate and 1 part of methacrylic acid, and a mixture of 0.25 parts of potassium persulfate and 5 parts of deionized water were each added separately for about 3 hours. Inject it, keep it at the same temperature for 1 hour, and then cool it to make the desired 2
A layered copolymer emulsion was obtained. The copolymer (A _1-1 ) is “Waters GPC200 type” (manufactured by Waters Co., USA).
As a result of measurement by GPC), it was approximately 6 × 10 ⁴ in terms of polystyrene, and this copolymer (A ₁ -
The Tg of 1) was approximately -5°C. Reference Example 2 (Preparation example of copolymer emulsion for comparison) 12 parts of ethyl acrylate, 5 parts of vinyl acetate, n
- 80 parts of butyl acrylate, 1 part of glycidyl methacrylate and 2 parts of methacrylic acid are uniformly mixed, and 2 parts of "Neogen R" are also present;
A copolymer emulsion consisting of only one layer was obtained according to a conventional method. Reference Example 3 (Preparation example of two-layer copolymer emulsion) First, 12 parts of ethyl acrylate, 5 parts of vinyl acetate
1 part of glycidyl methacrylate and 1 part of methacrylic acid were radically copolymerized according to a conventional method to obtain a copolymer emulsion consisting of only one layer. Next, in a separate reaction vessel, 80 parts of n-butyl acrylate and 1 part of methacrylic acid were radically copolymerized according to a conventional method to obtain a copolymerized emulsion consisting of only one layer. Both emulsions were then blended to obtain a mixture of copolymerized emulsions still consisting of only one layer. Reference Example 4 (Preparation example of two-layer copolymer emulsion) Same as Reference except that the monomer composition in the first stage reaction was changed to 12 parts of ethyl acrylate, 5 parts of vinyl acetate, and 2 parts of methacrylic acid. A copolymer emulsion having a two-layer structure but containing no epoxy groups in any of the copolymer layers was obtained in the same manner as in Example 1. Reference Example 5 (Preparation example of two-layer copolymer emulsion) Instead of glycidyl methacrylate, the same amount of N
- A copolymer emulsion having a two-layer structure but containing no epoxy groups in any of the copolymer layers was obtained in the same manner as in Reference Example 1 except for changing the use of methylol acrylate. Ta. Reference Example 6 (Preparation example of three-layer copolymer emulsion) In a reaction vessel similar to Reference Example 1, deionized water was added.
100 parts, 2 parts of "Neogen R", 5% FeCl ₃ 6H ₂ 0
3 parts of aqueous solution and 0.1 of sodium pyrosulfite
1 part of n-butyl acrylate, 3 parts of vinyl acetate, 1 part of glycidyl methacrylate, and 1 part of γ-methacryloxypropyltrimethoxysilane, and
A mixture of 0.1 part of ammonium persulfate and 5 parts of deionized water was injected separately over a period of about 1 hour, and the reaction was continued by holding the same temperature for another 1 hour to complete the first stage polymerization. Finished the reaction. Next, at the same temperature, a mixture of 20 parts of n-butyl acrylate and 2 parts of vinyl acetate, and a mixture of 0.1 part of ammonium persulfate and 0.1 part of sodium pyrosulfite were each injected over a period of about 1 hour. Then, the same temperature was further maintained for 1 hour to complete the second stage polymerization reaction. Furthermore, at the same temperature, a mixture consisting of 60 parts of 2-ethylhexyl acrylate, 0.2 parts of ammonium persulfate, and 0.2 parts of sodium pyrosulfite was injected over 2 hours, and then at the same temperature, 1 part of sodium pyrosulfite was injected.
The reaction was continued for a certain period of time and then cooled to obtain a copolymer emulsion having the desired three-layer structure. In addition, as a result of measuring the copolymer of n-butyl acrylate, vinyl acetate, glycidyl acrylate, and γ-methacryloxypropyltrimethoxysilane obtained in the first stage reaction with a "Waters GPC200 model", the polystyrene equivalent The copolymer had a Tg of about ^-40 °C. Reference Example 7 (Preparation example of copolymer emulsion for comparison) 33 parts of n-butyl acrylate, 5 parts of vinyl acetate
parts, 1 part glycidyl acrylate, 1 part and 2 parts of γ-methacryloxypropyltrimethoxysilane.
- Using 60 parts of ethylhexyl acrylate in the presence of 2 parts of "Neogen R", radical copolymerization was carried out according to a conventional method to obtain a copolymer emulsion consisting of only one layer. Examples 1 and 2 and Comparative Examples 1 to 5 Each of the copolymer emulsions obtained in each reference example was separately tested with an evaporation residue of 50% after drying.
g/m ² on a polyester film with a thickness of 25 μm using an applicator and dried at 110° C. for 10 minutes. Next, a pressure-sensitive adhesive sheet was prepared by leaving the coated surface exposed in a constant temperature and humidity room at 20° C. and 65% RH for one day and night. Afterwards, these various adhesive sheets were attached to a plasticized polyvinyl chloride adherend according to the method below, and then left in an atmosphere of 50°C x 85% RH to evaluate the cohesive force and adhesive force over time. The performance of the adhesive as a pressure-sensitive adhesive for plasticized polyvinyl chloride was comparatively investigated. Furthermore, the adhesion to plasticized polyvinyl chloride as a support was also comparatively investigated according to the following method. The results are summarized in Table 1, and the cohesive force, adhesive force, and adhesion were measured in the following manner. First, the cohesive force is - the above pressure sensitive adhesive sheet is 25mm
Cut to width so that the adhesive surface is 25mm x 25mm.
DOP was pasted on a polyvinyl chloride resin plate containing 50°C, and then the sample prepared in this way was left in an atmosphere of 60°C x 85% RH and taken out over time. ×65%
This was determined by hanging the weight vertically for 20 minutes in a constant temperature and humidity room at RH, then applying a dead load of 1 kg parallel to the bonded surface and measuring the time until the weight slipped off. It took time. Next, the pressure sensitive adhesive sheet cut to a width of -25 mm was moved back and forth once at a speed of 5 mm/sec with a 2 kg rubber roller on a polyvinyl chloride resin plate containing 50% DOP. The sample was left in an atmosphere of 50°C x 85°C RH, and was removed over time and peeled at a peeling angle of 180 degrees and a peeling speed of 200 mm/min. Furthermore, the adhesion was determined by the fact that the evaporation residue after drying was 25% for each copolymer emulsion separately.
g/m ² using a polyvinyl chloride film containing 50% DOP and an applicator, and then exposed the coated surface in a constant temperature and humidity room at 20°C x 65% RH. A pressure-sensitive adhesive sheet for the plasticized polyvinyl chloride support was prepared by leaving the adhesive sheet for a day and a night to dry.
After cutting it into 25mm width and pasting it on a stainless steel plate.
The state of peeling was determined visually by leaving it in an atmosphere of 50℃ x 80% RH and removing it over time, and visually judging the peeling condition. -○ indicates that this has occurred, -△ indicates that some peeling has occurred between the polyvinyl chloride and resin layer, and -x indicates that most of the peeling has occurred between the polyvinyl chloride and resin layer. did.

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Claims (1)

[Claims] 1 The dispersed particles constituting the copolymer emulsion, which is the main ingredient, consist of at least two layers, of which the (most) inner layer is composed of α,
0.1 to β-ethylenically unsaturated monomer (a-1)
10 parts by weight, and 0.1 to 20 parts by weight of an α,β-ethylenically unsaturated monomer (a-2) having a polar group reactive with the epoxy group in this monomer (a-1). and 99.8 to 70 parts by weight of other α,β-ethylenically unsaturated monomer (a-3) copolymerizable with (a-1) and (a-2) described above. 60 to 100 parts by weight of alkyl acrylate and/or alkyl methacrylate (a-4) having an alkyl group of C ₄ or more, which is the aggregate (A ₁ ) and whose (most) outer layer is Other copolymerizable α,β-ethylenically unsaturated monomers (a
-3) is a (co)polymer (A ₂ ) obtained from 0 to 40 parts by weight of the above copolymer (A ₁ ).
Characterized by a Tg of -40℃ to +20℃,
A pressure-sensitive adhesive for polyvinyl chloride molded products whose main ingredient is a multilayer copolymer emulsion.