JPS58145773A - Pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To provide a pressure-sensitive adhesive excellent in tackiness, cohesion, and adhesion over a wide temp. range, by incorporating two particular copolymer emulsions. CONSTITUTION:5-50wt% copolymer comprising an alpha,beta-ethylenically unsatd. monomer having a reactive polar group and an alpha,beta-ethylenically unsatd. monomer radical-polymerizable with said monomer and having no reactive polar group, said copolymer having Tg of -30-30 deg.C and weight-average MW of 5X10<3>-5X10<5> (in terms of PS) as determined by gel permeation chromatography, and 95-50wt% copolymer comprising 0.1-10pts.wt. alpha,beta-ethylenically unsatd. monomer having a polar group reactive with the reactive polar group involved in the above copolymer, 60-99.9pts.wt. alkyl (meth)acrylate having 4C or higher alkyl group, and 0-39.9pts.wt. alpha,beta-ethylenically unsatd. monomer radical-copolymerizable with either of these two are subjected to emulsion polymerization so as to obtain a solid content of 30-65wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and useful pressure-sensitive adhesive, and more specifically, the present invention relates to a new and useful pressure-sensitive adhesive, and more particularly, the dispersed particles of a copolymer emulsion serving as a main ingredient are copolymer emulsions each containing a reactive polar group. A copolymer containing a polar group that is reactive with this polar group and has excellent tack, cohesive force, and adhesion in a wide temperature range from low temperatures to room temperature. This invention relates to acrylic pressure-sensitive adhesives.

Rubber-based, silicone-based, and acrylic-based adhesives have been known as pressure-sensitive adhesives, and are widely used in adhesive tapes, adhesive sheets, and other various applications.

Among these, rubber-based pressure-sensitive adhesives have the disadvantage of poor weather resistance and aging resistance, and silicone-based adhesives have low cohesive strength, which can be improved by heat treatment at high temperatures. Although acrylic materials are used in various adhesive sheets as they have excellent weather resistance and aging resistance, on the other hand,
Since it is difficult to improve both adhesion and cohesive strength, pressure-sensitive adhesives have traditionally been used for different purposes, emphasizing their characteristics. In other words, for applications where particularly high cohesive force is required, acrylic polymers with increased molecular weight have been provided through crosslinking or selection of reaction conditions; However, only products with significantly reduced tack and low-temperature adhesion are available; on the other hand, for applications where this tack and low-temperature adhesion are particularly required, products with lower molecular weights are available. As a result, the cohesive force eventually decreases, and it has been an extremely difficult problem to keep the adhesive force and cohesive force at a high level in a well-balanced manner.

Furthermore, such acrylic pressure-sensitive adhesives have the disadvantage that their adhesive strength to polyolefins such as polyethylene and polypropylene is weak, particularly at low temperatures.

By the way, in recent years, polyolefins have been widely used as packaging materials, and with the spread of frozen foods, pressure-sensitive adhesives are also required to have both tackiness and adhesive strength for polyolefins at low temperatures. became.

Therefore, the object of the present invention is to achieve high levels of tackiness, adhesive force, and cohesive force, which were impossible to achieve with conventional pressure-sensitive adhesives based on acrylic polymers as described above. In addition to maintaining a good balance, it is particularly important to significantly improve the tackiness and adhesion to polyolefins over a wide temperature range from low temperatures to room temperature.

For this purpose, the present inventors have proposed that the dispersed particles constituting the copolymer emulsion as the main ingredient consist of at least two types of layers, at least one of which contains a reactive polar group. , a β-ethylenically unsaturated monomer (M,) and an α,β-ethylenically unsaturated monomer that does not contain a reactive polar group and is radically copolymerizable with the monomer (M,). copolymer (A,), and at least one other layer contains a polar group reactive with the reactive polar group in the copolymer (A,), α,β-ethylenically unsaturated Monomer (M) 0.1 to 105 parts by weight and alkyl acrylate and/or alkyl methacrylate 6 having an alkyl group having 4 or more carbon atoms
A copolymer (A2) of 0 to 999 parts by weight and 0 to 399 parts by weight of other α,β-ethylenically unsaturated extenders that can be radically copolymerized with these, and furthermore, the copolymer ( A,)'rg is between 13oC and 30oC, and
The weight average molecular weight in terms of polystyrene measured by permeation chromatography is 5X10'~
It is an object of the present invention to provide a pressure-sensitive adhesive based on a multilayer copolymer emulsion consisting of 5X1 [15].

Here, representative examples of the α,β-ethylenically unsaturated monomers M and M2 each containing a reactive polar group in the molecule include glycidyl acrylate, glycidyl methacrylate, or allyl glycidyl ether. Ephoxy derivative; vinyltriethoxysilane,
Vinyl silanes such as vinyltris(β-methoxyethoxy)silane or γ-methacryloxypropyltrimethoxysilane; Saturated carboxylic acids; acrylamide,
Vinyl amides such as methacrylamide, N-methylolacrylamide or N-methylolmethacrylamide; alcohol derivatives such as β-hydroxyacrylate or β-hydroxymethacrylate; or amine derivatives such as alkylaminoacrylate or alkylaminomethacrylate.

And these reactive polar group-containing monomers M, and M
Examples of the combination of 2 include Epoquin derivative-diunsaturated carboxylic acids or alcohol derivatives, or epoxy derivatives-vinylamides or amine derivatives, vinylsilanes-unsaturated carboxylic acids or alcohol derivatives, or vinylsilanes-vinylamides or amine derivatives. can be mentioned.

In addition, an alkyl (meth) having an alkyl group having 4 or more carbon atoms used for preparing the copolymer (A2)
Typical acrylates include n-butyl, i-butyl or t-butyl (meth)acrylate, n-amyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, ) acrylate or nonyl (meth)acrylate.

Furthermore, other radical copolymerizable α used to prepare the copolymers (A1) and (A2),
Typical examples of β-ethylenically unsaturated monomers include vinyl acetate, vinyl propionate, vinyl persate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, styrene, and (meth)acrylonitrile. , ethylene, propylene, butadiene or isoprene.

In obtaining the copolymer emulsion which is the main ingredient of the adhesive of the present invention, α
.

The appropriate molar ratio of the β-ethylenically unsaturated monomer (M, ) and (M2) is from 0.1 to 10.

Further, in obtaining this base emulsion, the ratio of the copolymer (AI) and copolymer (A2) to be used is preferably in the range of 5=95 to 50:50 by weight.

Furthermore, the bireactive polar group-containing monomer (Ml) and (M
When the total amount of the copolymers (A1) and (A2) is 100 parts by weight, the proportion of the copolymers (A1) and (A2) is preferably 9 parts each.

Furthermore, from the viewpoint of tackiness, cohesive force, adhesive force, and low-temperature physical properties of the finally obtained multilayer copolymer emulsion, the Tg of the copolymer (A,) is in the range of 30°C to 30°C. The weight average molecular weight of this copolymer (Aυ) in terms of polystyrene as measured by gel permeation chromatography is 5X105~
A range of 5XID'', preferably I x 10' to 2X10'' is suitable.

On the other hand, in providing the copolymer (A2) layer, the above-mentioned reactive polar group-containing monomer (M2) contains 01 to 10 parts by weight of an alkyl (meth) having an alkyl group having 4 or more carbon atoms. It is preferable to use 60 to 999 parts by weight of acrylate and 0 to 399 parts by weight of other α,β-ethylenically unsaturated oromonomers that can be radically copolymerized with these. Any known and commonly used emulsifier can be used in the preparation of the emulsifier, but the most representative ones include sodium dodecylbenzenesulfonate and alkaryl polyether. Anionic emulsifiers such as sulfates; nonionic emulsifiers such as polyoxyethylene nonylphenol ether or polyoxyethylene-polyoxypropylene block comonomers; cationic emulsifiers such as nilaurylpyridinium chloride or cetyltrimethylammonium bromide; Emulsifiers, etc.

Of course, if it can be done without using any emulsifier,
It can also be carried out by using a double-layered emulsifier and an emulsifying dispersant such as a water-soluble oligomer or polymer in combination.

1 In addition, the above t also copolymer emul/
? As the polymerization initiator used in preparing the polymer, known and commonly used initiators such as hydrogen peroxide, ammonium persulfate, potassium persulfate, t-butylhydroveroxide, etc. can be used, and furthermore, such polymerization initiators can be used. It may also be used in the form of a redox initiator in combination with known reducing substances such as ascorbic acid or sulfites.

In order to prepare the multilayer copolymer emulsion which is the main component of the adhesive of the present invention, conventionally known emulsion polymerization methods can be used; The solid content of this multilayer copolymer emulsion finally obtained is preferably 60 to 65% by weight, and the above-mentioned emulsifier or emulsifying dispersant is used in preparing the copolymer (A1). It is desirable to use it only in the step of
It is suitable that the copolymer (A2
) or these (A1) or (A2
) It can also be used by adding a small amount during multi-stage polymerization by repeating both radical copolymerization reactions to obtain both copolymers.

Such a multilayer copolymer emulsion comprises the copolymer (A
1) The copolymer (A2) layer is formed using the particles as cores, so that the copolymer (A2) is composed of at least two layers having these (A1) and (A2) as basic layer constituent units.

Of course, this means that it is not limited to two-stage polymerization, and the reactive polar group-containing monomer (Ml) or (M2) that can react with each other
It goes without saying that so-called multi-stage polymerization, in which the copolymerization reactions to obtain the respective copolymers (A1) or (A,) containing the above may be carried out repeatedly, may also be used.

Therefore, especially in the case of multi-stage polymerization, the material on top of the core copolymer (A) layer is always
It is easy to understand that the layers other than this 13-(A1) layer are simply the copolymer (A2) layer, but it is important to note that the layers other than the 13-(A1) layer are the third or higher layers in sequence. The third layer must not be a copolymer (A2) layer.
Layers other than this (A2) layer should simply be the copolymer (A1) layer, and similarly for the fourth layer of the whistle (A1
), it should simply be the (A2) layer.

According to this logic, the reactive polar group-containing monomer (Ml) or (M2) to be selected is one elemental system, that is, in the example of the combination of monomer groups as described above, vinylamides are selected for epoxy derivatives. It is not limited to the combination method based on the choice of using epoxy derivatives or amine derivatives, but it is also possible to use a multi-component system. It may be a combination of -, but only M
, or M214-, it is necessary to avoid using monomers that can react with each other in combination, and these M,
DoM2 is small (Tomo→S) between the layers through its polar group.
It is also necessary that the two react with each other.

The multilayer copolymer emulsion obtained in step 1 can be applied as it is to paper, cloth, plastics, film, etc., or the multilayer copolymer emulsion obtained in step 1 can be applied to paper, cloth, plastics, film, etc., or the multilayer copolymer emulsion obtained in step 1 can be coated with a main ingredient in steps 1 to 1, and if necessary, known methods. Conventional tackifiers, tackifiers, stabilizers, thickeners, pigments, fillers,
Appropriate amounts of plasticizers, wetting agents, or antifoaming agents may be added (
Regardless of how it is used, when the adhesive of the present invention is used, an adhesive with excellent tackiness, cohesive force, adhesive force, low-temperature physical properties, etc. can be obtained.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In the following, all parts are by weight. Example 1 Reaction using a stirrer, condenser, thermometer, and dropping funnel In a container, add 100 parts of deionized water and [Neogen R
1 (emulsifier manufactured by Daiichi Kogyo Seiyaku ■) were added and stirred.

The internal temperature was maintained at 80℃, and nitrogen gas was introduced into the container.
~ Then, a mixture of 10 parts of ethyl acrylate, 5 parts of vinyl acetate, 0.5 parts of glycidyl methacrylate and 0.1 part of lauryl mercaptan, and 0.25 parts of potassium persulfate.
A mixture of 5 parts of deionized water and 5 parts of deionized water was injected separately for about 30 minutes and then maintained at the same temperature for 1 hour to complete the first stage polymerization reaction.

After that, at the same temperature, n-butyl acrylate-1.84
A mixture of 0.65 parts of potassium peroxide and 0.65 parts of methacrylic acid, and a mixture of 0.25 parts of potassium peroxide and 5 parts of deionized water were each injected over a period of about 2 hours, and then kept at the same temperature for 1 hour. After holding and cooling, the desired two-layer copolymer emulsion was obtained.

In addition, the weight average molecular weight of the copolymer from ethyl acrylate, vinyl acetate, glycidyl methacrylate, and lauryl mercaptan in the first stage reaction was measured with "Waters GPC 200 model" (gel permeation chromatography manufactured by Waters, USA). The result was about 5×10' in terms of polystyrene, and the Tg was about -5°C.

Comparative Example 1 10 parts of ethyl acrylate, 5 parts of vinyl acetate, 84 parts of n-butyl acrylate, 05 parts of glycidyl methacrylate
parts, 05 parts of methacrylic acid and 0 parts of lauryl mercaptan
One part of the mixture was uniformly mixed and subjected to radical copolymerization according to a conventional method in the presence of two parts of "Neogen R" to obtain a copolymer E17-Mulsion for comparison.

Comparative Example 2 First, 10 parts of ethyl acrylate, 5 parts of vinyl acetate, 085 parts of glycidyl methacrylate, and 01 part of lauryl mercaptan were radically copolymerized according to a conventional method, and then the copolymer emulsion obtained here was copolymerized with 84 parts of n-butyl acrylate. A blended emulsion was obtained by blending a copolymer emulsion obtained by radical copolymerizing 1 part and 05 parts of acrylic acid according to a conventional method.

Example 2 Into a reaction vessel similar to Example 1, 100 parts of deionized water and 2 parts of "Neogen R" were charged, and the internal temperature was adjusted to 80°C.
and separately a mixture of 10 parts of n-butyl acrylate, 0.5 parts of glycidyl methacrylate and 0.3 parts of lauryl mercaptan, and a mixture of 0.2 parts of potassium persulfate and 5 parts of deionized water, It took about 1 hour for the injection punch to be applied, and the first stage polymerization reaction was further heated to the same temperature for 1 hour to complete the first stage polymerization reaction.

Then, at the same temperature, a mixture of 60 parts of 2-ethylhexyl acrylate, 28 parts of n-butyl acrylate and 15 parts of methacrylic acid, 0.2 parts of potassium persulfate and 5 parts of deionized water was added. were injected separately over a period of 2 hours, kept at the same temperature for 1 hour, and then cooled to obtain the desired two-layer copolymer emulsion.

In addition, the weight average molecular weight of the copolymer consisting of n-butyl acrylate, glycidyl methacrylate, and lauryl mercaptan in the first stage reaction as calculated by gel permeation chromatography in terms of polystyrene is about 2 x 104, and the Tg is about 20°C. Met.

Comparative Example 6 The composition of the monomers (including lauryl mercaptan) was the same as in Example 2, and these were uniformly mixed and subjected to radical copolymerization according to a conventional method in the presence of 2 parts of 1 Neogen R. Finally, a copolymer emulsion for comparison was obtained.

Example 1 In a reaction vessel similar to Example 1, 100 parts of deionized water,
[Charge 2 parts of Neogen RJ, 3 parts of 5% FeCl3.6H20 aqueous solution, and 2 parts of sodium pyrosulfite, keep the internal temperature at 70°C, and add 5 parts of ethyl acrylate,
Injecting separately a mixture of 10 parts of vinyl acetate, 1 part of acrylic acid and 0.2 parts of lauryl mercaptan, and a mixture of 0.2 parts of ammonium persulfate and 5 parts of deionized water over a period of about 1 hour; The same temperature was further maintained for 1 hour to complete the first stage polymerization reaction.

Next, at the same temperature, a mixture consisting of 60 parts of 2-ethylhexyl acrylate, 24 parts of ethyl acrylate, and 0.1 part of γ-methacryloxypropyltrimethoxysilane, 0.2 parts of ammonium persulfate, and 0.2 parts of sodium pyrosilisulfate was added. and a mixture consisting of each separately,
The mixture was injected over 2 hours, kept at the same temperature for 1 hour, and then cooled to obtain the desired two-layer copolymer emulsion.

In addition, the weight average molecular weight in terms of polystyrene due to the gel permeation of co-offshore σ from ethyl acrylate, vinyl acetate, acrylic acid, and lauryl mercaptan in the first stage reaction is approximately 5×10', and Tg
is approximately 15°C.

Comparative Example 4 29 parts of ethyl acrylate, 11 parts of vinyl acetate (,2
- 60 parts of ethylhexyl acrylate, 1 part of acrylic acid
part, 21- γ-methacryloxypropyltrimethoxysilane 0.1
1 part and 02 parts of lauryl mercaptan were mixed and radical copolymerized in the presence of 2 parts of "Neogen R" according to a conventional method to obtain a copolymer emulsion for comparison.

Application Examples 1 to 3 and Comparative Application Examples 1 to 4 Each of the copolymer emulsions obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was separately dried to have an evaporation residue of 300 E//m2. It was applied onto a polyester film having a thickness of 25 μm using an applicator and dried at 110° C. for 20 minutes.

Next, a pressure-sensitive adhesive sheet was prepared by leaving the coated surface in a constant temperature and humidity chamber at 20° C. and 65% RH for one day in a mist state.

Measurement of tackiness, adhesive force and cohesive force of these various adhesive sheets 1. Ta. The results are summarized in Table 1.

=22- In addition, each test method was conducted in accordance with the procedures described below.

Adhesiveness - J, ball rolling test according to the Dow method -
The test was carried out at three points: 10°C, 0°C and 20°C.

To the stainless steel plate of 60uX4CJ, 2; 7
Pressed back and forth with a rubber roller, then heated at 40°C16
It was hung vertically for 20 minutes in a thermostatic chamber at 5% RH, and then a dead load of 1 kg was applied parallel to the adhesive surface, and the time until the weight slipped off was measured. I used it as power.

The adhesive car sample (pressure-sensitive adhesive sheet) was cut into 25mm x 25mm pieces, and each was applied with two rubber rollers to a stainless steel plate, a polyethylene plate, and a polypropylene plate in a temperature atmosphere of -10°C, 0°C, and 20°C. The adhesive force was measured by pressing at a speed of 5 mm/sec for 20 minutes, then peeling at a peeling angle of 180 degrees and a peeling speed of 500 mm/min.

hmm =24-

Claims (1)

[Claims] The dispersed particles constituting the copolymer emulsion as the main ingredient are composed of at least two or more types of multilayers, and at least one of the layers contains a reactive polar group.
, β-ethylenically unsaturated monomer (Ml) and the monomer (M
, ) and a radically copolymerizable α,β-ethylenically unsaturated monomer containing no reactive polar group (A
I), and at least one other layer is made of the copolymer (
A, β-ethylenically unsaturated monomer (M2) containing a polar group reactive with the reactive polar group in (M2) 0.1 to
10 parts by weight, 60 to 999 parts by weight of alkyl acrylate and/or alkyl methacrylate having an alkyl group having 4 or more carbon atoms, and 0 to 999 parts by weight of other α,β-ethylenically unsaturated monomers that can be radically copolymerized with these. 399
k) is a copolymer (A2) with parts by weight, and the Tg of the copolymer (A,) is between 160°C and 30°C, and
The weight average number of molecules in terms of polystyrene measured by gel permeation chromatography is 5X1
A pressure-sensitive adhesive having a multilayer copolymer emulsion as a main ingredient, characterized in that it has a particle size of 0' to 5 x 105.