JPH0791516B2 - Ethylene / vinyl acetate / dioctyl-maleate / 2-ethylhexyl-acrylate-copolymer - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates generally to pressure sensitive adhesive compositions, and in particular to a method of making the same suitable for use on vinyl substrates. The resulting adhesive consists of a polymer of ethylene, vinyl ester, di-2-ethylhexyl maleate or their corresponding fumarates, 2-ethylhexyl acrylate and unsaturated monocarboxylic acids.

[Problems to be Solved by the Prior Art and Invention] The pressure-sensitive adhesive has a function of providing instant adhesion when applied under slight pressure. They have built-in properties which ensure that they adhere to the surface without any activation treatment such as treatment with solvent or heat and, moreover, before the bond between the adhesive and the surface breaks. It is characterized by having sufficient internal strength that the adhesive does not break. The ability to obtain instant adhesion is commonly expressed as the amount of "tack" or "tackiness". It is generally desirable to obtain as much tack as possible without losing a significant amount of internal strength (cohesiveness). This balance of adhesiveness and cohesiveness is obtained in adhesive polymers, as it is common to incorporate monomers into the polymer to increase cohesive strength, which generally reduces the tackiness of the adhesive. Was difficult.

Special types of pressure sensitive adhesives are used in automotive vinyl rooftops, decorative ornaments such as in vinyl labels and decals and vinyl substrates utilized in a wide variety of industrial applications such as in special types. It Unlike common polyolefin-based films such as polyethylene and polypropylene, these polyvinyl chloride (PVC) -films require many additives to be prepared due to the properties required for their processing and high glass transition temperatures. . Some of these additives are mobile components and serve long-term vinyl decals or labels. A wide range of vinyl properties can be obtained because the amount and type of additives vary in the vinyl formulation. Typical flexible PVC
The film preparation contains many additives including plasticizers. Plasticizers used include mobile monomer types such as phthalate esters (eg dioctyl phthalate) or slightly mobile polymeric plasticizers (eg polyesters, epoxidized soybean oil). These applications place stringent demands on the adhesive composition. In particular, vinyl substrates contain large amounts of these plasticizers that tend to migrate into the adhesive, which migration, especially after aging, causes the bond to collapse and the bond to fail. .

Therefore, adhesive coated flexible polyvinyl chloride-
The use of films has been customarily plagued to varying degrees by degrading properties as the plasticizer migrates from the PVC-film to the adhesive coating. The degree to which this occurs depends on the PVC formulation and adhesive used. In addition to the migration resistance (migration resistance) of this plasticizer during aging, the adhesives used for vinyl decals must have a high initial peel value, both cohesive and adhesive strength were first mentioned. Must be controlled and the shrinkage resistance must be suppressed.

Some of the problems encountered with pressure sensitive adhesives are particularly exemplified in the field of adhesive coated plasticized vinyl (PVC) substrates, which are significantly affected by the type and amount of plasticizer in the PVC film. . These adhesives, which allow the use of PVC for flexible applications, are a major cause of degradation of polymer coatings applied to PVC. As a result of their greater mobility, monomeric plasticizers have a greater effect on adhesion than polymeric plasticizers. Everything else being the same, more decay is experienced as a function of time in adhesive coated decals when vinyl films contain high amounts of monomer plasticizer. This issue is addressed by our US Pat. No. 4,753, granted on June 28, 1988.
No. 3,846 is presented. Although the claimed composition of this U.S. patent is superior to the prior art, there is still room for improvement in cohesive strength properties for certain applications involving vinyl substrates.

According to the present invention, the inventor has found that 25-40% by weight of vinyl ester of alkanoic acid, 10-30% by weight of ethylene, 20-30%
Wt% di-2-ethylhexyl-maleate or-
A pressure sensitive adhesive characterized by an excellent balance of adhesiveness and cohesiveness from an emulsion copolymer containing fumarate, 20 to 30% by weight of 2-ethylhexyl acrylate and 1 to 5% by weight of unsaturated monocarboxylic acid. It has been found that can be manufactured. There are limitations to the use of special semi-batch emulsion polymerization methods during the preparation of this adhesive. According to this, the ethylene and vinyl esters are initially introduced together with preferably 50% to 70% of the relatively small reactive maleate monomer. The highly reactive acrylate monomer, the remaining maleate and other functional monomers are then added incrementally during the polymerization process.

The resulting adhesive is characterized by an overall balance of adhesion and cohesiveness even after storage of the adhesive coated substrate. As such, this pressure sensitive adhesive requires special applications for adhering vinyl substrates and, in particular, a combination of high peelability and tackiness and excellent cohesiveness to prevent vinyl shrinkage in the liner. Used as an adhesive for vinyl decals.

The vinyl ester used in the present invention has 1 to about 13 carbon atoms.
Is an ester of alkanoic acid. Representative examples include: vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl-2-ethyl-hexanoate, vinyl isoocta. Noate, vinyl nonate, vinyl decanoate, vinyl pivalate, vinyl versatate, etc. Of the above, vinyl acetate is particularly advantageous because it is readily available and inexpensive.
The vinyl ester is present in the copolymer in an amount of about 25-40% by weight, especially 30%.
Present in an amount of ~ 35% by weight.

A particular dioctyl maleate isomer used in the present invention is di-2-ethylhexyl maleate. Since the structures of the fumarate and the maleate (cis isomer) are the same after polymerization, the corresponding fumarate esters could also be used in the present invention. This component is about 20-30 in the copolymer.
It is present in an amount of% by weight, especially 30% by weight.

Further, in the present invention, 2-ethylhexyl acrylate is 20 to
30% by weight, especially about 25% by weight and about 10% ethylene.
-30% by weight, in particular 15-25% by weight.

Unsaturated monocarboxylic acids used in the present invention include, for example, half esters of acrylic acid and methacrylic acid or maleic acid, such as monoethyl-, monobutyl- or monooctyl maleate, preferably monoethyl maleate.
Contains along with acrylic acid. The acid is present in an amount of 1-5% by weight, especially 2-4% by weight.

It may also be advantageous to incorporate minor amounts of one or more functional copolymer monomers into the copolymer. Suitable copolymerizable monomers include, for example, acrylamide, tert-octylacrylamide, N-methylol (meth) -acrylamide, N-vinylpyrrolidinone, diallyl adipate, triallyl cyanurate, butanediol diacrylate, allyl methacrylate and the like. C ₂ -C ₃ - hydroxy acrylate - esters, such as hydroxyethyl acrylate, hydroxypropyl acrylate and the corresponding methacrylates. These copolymerizable monomers are generally used in amounts less than about 5%, depending on the nature of the individual copolymerizable monomers. In all cases, the Tg of the resulting pressure sensitive adhesive should be in the range of about -45 to -25 ° C. Any copolymerizable monomer should not be added in such an amount that a polymer above this Tg range is obtained.

In addition, certain copolymerizable monomers that aid in the stability of the copolymer emulsion, such as vinyl sulfonic acid, can also be used as latex stabilizers. These are optionally present-when used-monomers are from 0.1 to about 2% by weight of the monomer mixture.
Is added in a very small amount.

In any of the methods utilized in the present invention, vinyl acetate, ethylene, maleate and acrylate monomers are polymerized in an aqueous medium under pressure not exceeding 100 atm in the presence of a catalyst and at least one emulsifier, At that time, the aqueous system is maintained at pH 2 to 6 by a suitable buffer,
The catalyst is added incrementally or continuously. More preferably, 50-75% of vinyl acetate and maleate are suspended in water and a solution of ethylene in vinyl acetate and maleate is present in the reaction zone under polymerization pressure in the presence of ethylene. Stir well to the practical limit of solubility at and while gradually heating the vinyl acetate and maleate to the polymerization temperature. During the equalization period,
It is followed by a polymerization period in which the catalyst, which may consist of the main catalyst or initiator-which may contain activators-is added incrementally or continuously with the acrylate and the remaining maleate or functional monomer. The monomers used can be added either as pure monomers or as premixed emulsions.

Suitable as polymerization catalysts are the water-soluble free radical formers commonly used in emulsion polymerization, such as hydrogen peroxide, sodium persulfate, potassium persulfate and ammonium persulfate, and tert-butyl hydroperoxide, The amount used is 0.01 to 3% by weight, in particular 0.01 to 1% by weight, based on the total weight of the emulsion. These may be used alone or in reducing agents such as formaldehyde-sodium sulfoxylate, ferrous salts, sodium dithionite, sodium bisulfite, sodium sulfite,
As a redox catalyst together with sodium thiosulfate, 0.01 to 3% by weight, based on the total amount of emulsion, in particular 0.
It can be used in an amount of 01 to 1% by weight. The free radical former may be charged to the aqueous emulsion solution or may be metered in during the polymerization.

The polymerization is carried out at pH-values of 2 to 7, especially 3 to 5. This pH
In order to maintain the zone, it is advantageous to work in the presence of conventional buffer systems, such as alkali metal acetates, alkali metal carbonates, alkali metal phosphates. Polymerization regulators such as mercaptans, aldehydes, chloroform, ethylene chloride and trichlorethylene may be added in this case.

Emulsifiers include those commonly used in emulsion polymerization as well as protective colloids that may optionally be present. The emulsifiers can be used alone or in a mixture with protective colloids.

The emulsifiers are anionic, cationic, nonionic surface-active compounds or mixtures thereof. Suitable anionic emulsifiers include, for example, alkyl sulphonates, alkylaryl sulphonates, alkyl sulphates,
There are sulfates of hydroxyalkanols, alkyl- and alkylaryls, -disulfonates, sulfonated fatty acids, sulfates and phosphates of polyethoxylated alkanols and of polyethoxylated alkylphenols and esters of sulfosuccinic acid. Suitable cationic emulsifiers include, for example, alkyl quaternary ammonium salts and alkyl quaternary phosphonium salts. Examples of suitable nonionic emulsifiers are straight-chain and branched-chain alkanols having 6 to 22 carbon atoms or alkylphenols or higher fatty acids or higher fatty acid amides or first- and second-higher There are addition products in which 5 to 50 moles of ethylene oxide are added to alkylamines, and block copolymers of ethylene oxide and propylene oxide and mixtures thereof. If a combination of emulsifiers is used, it is advantageous to use it in combination with a relatively hydrophilic emulsifier of a relatively hydrophobic emulsifier. The amount of emulsifier is generally about 1 to about 1 of the monomers used during polymerization.
0, especially about 2 to about 8% by weight.

The emulsifiers used in the polymerization can also be added in their entirety in the first introduction to the polymerization zone or in part of the emulsifier, for example 90 to
25% by weight may be added continuously or batchwise during the polymerization.

Various protective colloids may be used in place of or in addition to the above emulsifiers. Suitable protective colloids include partially acetylated polyvinyl alcohol, eg up to 50% acetylated, casein, hydroxyethyl starch,
Carboxymethyl-cellulose, gum arabic and
Included are these analogs as known in the synthetic emulsion polymerization art. Generally, these colloids are used in amounts of 0.05 to 4% by weight, based on the total weight of the emulsion.

The method of making the copolymers of the present invention generally comprises making an aqueous solution containing at least some emulsifier and stabilizer and a pH buffer system. This aqueous solution and the first charge of vinyl ester and maleate are introduced into the polymerization vessel and the ethylene pressure is brought to the desired value. The amount of ethylene that gets into the copolymer is affected by pressure, agitation and the viscosity of the polymerization medium. Therefore, high pressure is used to increase the ethylene content of the copolymer. A pressure of at least about 10 atmospheres is most advantageously used. As mentioned above, the mixture is thoroughly stirred to dissolve the ethylene and continue stirring until substantial equilibrium is achieved. This generally requires about 15 minutes. However, shorter times may be required depending on the vessel, stirring efficiency, individual system, etc. If high ethylene content is required,
High speed stirring should be used. In each case, by measuring the ethylene pressure drop in a conventional manner,
The realization of substantial equilibrium can be easily ascertained. Conveniently the charge is brought to the polymerization temperature during the stirring period. Agitation can be accomplished by shaking, by a stirrer, or by other known mechanisms. The polymerization is then started by introducing an initial amount of catalyst and, if used, activator. After initiating the polymerization, the catalyst and activator are added incrementally as needed to continue the polymerization. And acrylate, the remaining maleate and other minor amounts of functional monomers are added as well.

The polymerization reaction generally continues until the residual vinyl ester monomer content is less than about 1%. The completed reaction product may then be cooled to about room temperature while being sealed from the atmosphere.

Adhesive emulsions may be prepared and diluted with water if desired, but with a relatively high solids content, such as
It is used with a solids content not lower than 35-70%, preferably 50%.

The particle size of the latex particles can be controlled by the amount of nonionic or anionic emulsifier or by the amount of protective colloid used. To obtain a small particle size, a relatively large amount of emulsifier is used. Generally, using a relatively large amount of emulsifier results in a relatively small average particle size.

If desired, customary additives may be incorporated into the inventive adhesives in order to modify the properties of the novel inventive adhesives. Among these additives are thickeners, fillers or pigments such as talc and chalk, small amounts of tackifiers and the like.

Emulsion adhesives are useful on any conventional tape or other planar material, particularly vinyl substrates such as vinyl films or sheets. The adhesive can be applied using conventional methods. As a typical method, the adhesive is applied to the release liner by a mechanical application method of an adhesive, for example, air knife coating, trailing blade coating, doctor blade coating, reverse rotation roll coating or gravure coating method. The adhesive is dried at room temperature and then about 250 °
Oven dry at F for 10 minutes. The coated release liner may then be laminated to the planar material by a nip roll using pressure between a rubber roll and a steel roll.
This technique achieves transfer of adhesive to planar materials with minimal penetration.

Example 1 This example illustrates the polymerization process used to make the pressure sensitive adhesives of the present invention.

In a 10 l autoclave, 450 g (of a 20% w / w solution in water) alkylaryl-polyethylene oxide sodium sulphate (3 mol ethylene oxide added), 40 g (70% w / w concentration in water) Alkylaryl-polyethylene oxide (in solution) (addition of 30 mol ethylene oxide), 90 g sodium vinyl sulphonate (in 25% W / W strength solution in water), 0.5 g sodium acetate, 2 g formaldehyde-sulphoxyl Sodium acid, 5 g of ferrous sulphate solution (of a 1% W / W strength solution in water) and 2250 g of water are introduced. After purging with nitrogen, 2000 g vinyl acetate and 500 g di-2
Charge the reactor with ethylhexyl maleate. The reactor was then pressurized to 700 psi with ethylene and 50 minutes for 15 minutes.
Equilibrate at ° C. Polymerization was then carried out by metering a solution of 40 g of tert-butylhydroxyperoxide in 250 g of water and a solution of 25 g of formaldehyde-sodium sulfoxylate in 250 g of water over 5 1/2 hours. And start.

When an exothermic reaction of 2 ° C occurs, 500 g of di-2 is added to 400 g of water.
-Ethylhexyl maleate, 1000 g of 2-ethylhexyl acrylate, 100 g of acrylic acid, 4 g of dodecyl mercaptan, 1 g of sodium acetate, 300 g of alkylaryl-polyethylene oxide sodium sulphate (at 20% W / W in water) An emulsion obtained by pre-emulsifying (adding 3 moles of ethylene oxide) and 40 g (dissolving 70% W / W concentration in water) of alkylaryl polyethylene oxide (adding 30 moles of ethylene oxide) to an autoclave Add evenly over 1/2 hour.

The reaction temperature is raised to 70-75 ° C. over 1 hour and maintained during the polymerization by external cooling. When the initiator has been added slowly, the product is transferred to a depressurized vessel to remove residual ethylene from the system. This product is referred to as Emulsion 1.

Using the general procedure described above, another emulsion is prepared with varying amounts and / or monomer composition. The major and / or minor monomers used and the individual amounts for each are shown in Table 1. In particular, Examples 1, 2 and 3 varied the amount of vinyl acetate and dioctyl maleate and
-Shows a semi-batch process with the advantageous method of adding 50% of ethylhexyl maleate first and the remaining 50% slowly. Example 16 is a repeat of Example 2. Examples 4 and 5 are two extremes in which all di-2-ethylenehexyl maleate is added first or all slowly. For the purpose of further comparison, Example 6 represents a representative of the prior art slow addition method, while Examples 7 and 8 are slow addition or semi-batch prepared acrylate / EVA compositions (maleate free). ) Is shown. Example 9 shows a maleate / EVA composition (without 2-ethylhexyl acrylate) prepared by the batch process. Examples 10 and 11 show a vinyl acrylic product and a competing free acrylic product for comparison. Examples 12, 13, 14 and 15 illustrate the advantages of the process of the invention using different functional (small amounts) monomers and carboxyls and / or varying the amount of carboxyl functionalities. ing.

The emulsion adhesive is then applied to the plasticized vinyl film and dried in an oven at 105 ° C for 5 minutes. The resulting dry adhesive has a coverage of 20 mg / in ² . This coating is then applied to the Pressure Sensitive Tape Coun
cil), and the peel strength is tested according to Test Method No.1. However, the point that the dwell period from when the coating is placed in contact with the stainless test panel to when the peel strength test is performed is changed. In addition, the bonded specimens are heat aged as shown in Table II to promote the tendency for loss of adhesion upon aging on PVC substrates to move the plasticizer into the polymer. Aging peel test is 70 ℃
Aged for 7 days and 20 minutes and 24 respectively
Conduct after the time recovery time. The percent shrinkage was measured after aging on a release liner at 70 ° C for 24 hours.

A test was also conducted to evaluate the viscoelasticity of the polymer. This viscoelasticity is space for dynamic mechanical analysis (using a rheometer) of polymer solids and shows the relationship between polymer structure and product performance. This analysis, among other things, simultaneously measures materials that respond to both elastic and viscous stresses. Some quantities can be calculated from the measured strain and stress.
If the test is conducted in shear geometry, the shear module (G) is calculated. The tensile and bending tests measure the tension module (E).

For dynamic mechanical analysis, the film is cast on release paper, air dried for one day and then placed in a 60 ° C. oven for two days. The final thickness of the film is about 2 mm. Often, to obtain frequency sweeps, probe at 0.1 to 100 Rad / sec room temperature (25 ° C) at a fixed strain (10%) of the film. The storage module (G '), biscol module (G ") and complex viscosity (ETA) are then plotted.

The elastic module (G 'or E') of a material is defined as the ratio of elastic (internal phase) stress to strain and is related to the material's ability to store elastic energy. Similarly, the substance loss module (G "or E") is the ratio of viscous (out of phase) components to strain and is related to the ability of the substance to dissipate stress during heating. The ratio of these modules (G ″ / G ′ or E ″ / E ′) is defined as tan Δ and indicates the relative degree of viscous and elastic dissipative properties or material damping. The complex viscosity (ETA) can be defined by the shear module. This viscosity can be related to the viscosity measured in the stable shear test by the relationship known as Cox-Merz law.

Suitable polymers for use in pressure sensitive adhesive applications should be highly viscoelastic materials. Therefore PSA is 1rad /
It should have an elastic module (G ') level of 5 × 10 ^{4 to} 2 × 10 ⁵ in s. This provides sufficient deformation for the new material to flow well at short contact times. It also has sufficient rigidity for low creep characteristics over a long period of time.

The results set forth in Table II show that the adhesive properties of the polymers of the invention are excellently retained (compared to the prior art) when the PVC-film (vinyl) is subjected to aging. There is. This is illustrated in particular by Examples 1, 2, 3 and 16 and especially by Examples 2 and 16. The latter shows a high initial peel strength (3-4 lbs) and 3
Compared to the current state of the art EVA acrylates and vinyl acrylics, which show an initial peel strength of ~ 4 lbs and a low retention of only 1-2 lbs of peel strength when aged.
A peel strength of 2.5-3 lbs is retained when aged.

The test results also show that functional monomer is required where initial peel strength is desired (Examples 2, 12, 13, 14, which show the effect of varying the amount of functional monomer). 15 and 16
reference).

The test results also show that the polymerization method described in Example 2 in which the dioctyl maleate charge is distributed in approximately equal amounts in the initial introduction and the slower additional introduction is particularly advantageous. This method is characterized by high initial peel strength (> 3.5 lbs), good retention on aging (> 2.5 lbs) and low shrinkage on liner (less than or equal to 1% CD or MD) Provides a pharmaceutical polymer. Also, Example 4 (all dioctyl maleate added first),
The adhesive polymer features of Example 2 observed when compared to Example 5 (slowly add dioctyl maleate) and Example 6 (slowly add all monomers) were as follows. It is shown in the rheological evaluation of elasticity.

tan Δ G ′ × 10 ⁵ G ″ × 10 ⁵ ETA × 10 ⁶ Example 2 0.68 2.24 1.52 2.70 Example 4 0.81 1.04 0.84 1.34 Example 5 0.52 1.71 0.89 1.93 Example 6 0.56 1.04 0.58 1.19 Above in detail in an advantageous embodiment of the invention Although the modifications and improvements thereof will be easily understood by those skilled in the art, the idea and scope of the present invention are limited by the claims and not by the above-described embodiments.

The present invention relates to a copolymer, a pressure-sensitive adhesive and a method for producing the same according to the claims, and the embodiments include the following: 1) A polyvinyl chloride substrate is plasticized with a mobile plasticizer. The substrate according to claim 1, which is

2) The substrate according to item 1 above, wherein the plasticizer is a phthalate ester or polyester or epoxidized soybean oil.

3) The vinyl ester in the pressure sensitive adhesive is vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl-2-ethyl-hexanoate, vinyl isooctano. Selected from the group consisting of art, vinyl nonate, vinyl decanoate, vinyl pivalate and vinyl versatate, and these esters in the adhesive 30
The substrate of claim 1 present in an amount of ˜35% by weight.

4) Di-2-ethylhexyl maleate is used and is present in the adhesive in an amount of about 25% by weight and 2
A substrate according to claim 1, wherein the ethylhexyl acrylate is present in an amount of about 25% by weight.

5) The substrate according to claim 1, wherein the acid in the adhesive is acrylic acid or monoethyl maleate.

6) The adhesive according to claim 2, wherein the vinyl ester is vinyl acetate, the maleate is di-2-ethylhexyl maleate, and the copolymerizable monomer is hydroxyethyl acrylate or hydroxypropyl acrylate.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C09J 131/02 JCZ 133/08 JDE 135/02 JDE

Claims (4)

[Claims] 1. A vinyl ester of alkanoic acid of 25-40% by weight, 10-30% by weight of ethylene, 20-30% by weight of di-2-.
Ethylhexyl-maleate or fumarate, 20-30
Wt% 2-ethylhexyl acrylate and 1-5
In a plasticized polyvinyl chloride substrate coated with a pressure sensitive adhesive composition containing wt.% Unsaturated monocarboxylic acid, the adhesive was prepared using a semi-batch emulsion polymerization technique and used all maleate or fumarate monomers. 50-75% of which is initially introduced with all of the ethylene and vinyl esters, and the remaining maleate or fumarate is added incrementally along with the acrylate and unsaturated monocarboxylic acid monomer during the polymerization. The plasticized polyvinyl chloride substrate as described above. 2. The adhesive additionally comprises acrylamide, tert-octylacrylamide, N-methylol (meth) acrylamide, N-vinylpyrrolidinone, diallyl adipate, triallyl cyanurate, butanediol-diacrylate, allyl methacrylate. Containing up to 5% by weight of at least one copolymerizable monomer selected from the group consisting of, hydroxyethyl acrylate, hydroxypropyl acrylate and their corresponding methacrylates and the amount of the copolymerizable monomer being an adhesive. -45 to
The substrate of claim 1 in an amount sufficient to maintain it in the Tg range of -25 ° C. 3. Substantially 25-40% by weight of vinyl ester of alkanoic acid, 10-30% by weight of ethylene, 20-30% by weight of di-2-ethylhexyl-maleate or -fumarate, 20-30% by weight. 2-ethylhexyl acrylate,
1-10 wt% unsaturated monocarboxylic acid monomer and acrylamide, N-methylol (meth) -acrylamide, N-vinylpyrrolidinone, diallyl adipate, triallyl cyanurate, butanediol diacrylate, tertiary octyl acrylamide To be applied to a plasticized polyvinyl chloride film consisting of 0 to 10% by weight of at least one copolymerizable monomer selected from the group consisting of hydroxyethyl acrylate, hydroxypropyl acrylate and their corresponding methacrylates. A suitable pressure sensitive adhesive composition having a Tg of -45 to -25 ° C, prepared using a semi-batch emulsion polymerization technique,
Of the total maleate or fumarate monomers used, 50-75% are first introduced together with all of the ethylene and vinyl esters, and the remaining maleate or fumarate together with the acrylate and unsaturated monocarboxylic acid. The pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition is added gradually in the course of polymerization. 4. Polymerizing using a semi-batch emulsion polymerization technique,
25-40 wt% vinyl ester of alkanoic acid, 10-30 wt% ethylene, 20-30 wt% di-2-ethylhexyl-maleate or -fumarate, 20-30 wt% 2
In preparing the pressure-sensitive adhesive composition as a copolymer consisting of ethylhexyl acrylate and 1 to 5% by weight of unsaturated monocarboxylic acid, all ethylene and vinyl esters are used first, the total maleate or fumarate units. A sensation characterized in that it is introduced together with 50% to 75% of the body and the remaining maleate or fumarate is added incrementally in the course of the polymerization together with the acrylate and unsaturated monocarboxylic acid monomers. A method for producing a pressure-sensitive adhesive composition.