JPH0762007A - Production of aqueous emulsion, and pressure-sensitive agent - Google Patents

Abstract

PURPOSE:To produce an emulsion capable of providing a pressure-sensitive agent having high adhesiveness, retaining force and tackiness by successively charging ethylene, an unsaturated carboxylic acid ester, an vinylester and an olefinic monomer into a polymerization system. CONSTITUTION:This emulsion contains (A) 5-30wt.% of ethylene, (B) 20-85wt.% of an alpha,beta-unsaturated carboxylic acid ester of formula I (R1 is II or methyl; R2 is 1-18C alkyl), (C) 10-75wt.% of a vinylester of formula II (R3 to R5 are H or alkyl, with the proviso that total carbon numbers are <=18) and (D) 0.3-8 pts.wt. (based on 100 pts.wt. of the components B+C) of a copolymerizable olefinic monomer having carboxyl, an amide, N-methylol, an epoxy and hydroxy. 10-50% (based on total amount to be charged) of components B+C is charged into polymerization system and then, charge of the component D is started and charge amount of the component D in the point when total amount of the components B+C to be charged is charged is set to 50-90% based on total amount of the component D to be charged and then, residual amount of the component D is charged to complete the polymerization.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an aqueous emulsion and a pressure-sensitive adhesive.

[0002]

2. Description of the Related Art High adhesive strength, holding strength and adhesive strength are one of the most important characteristics required of pressure-sensitive adhesives. An ethylene-vinyl ester- (meth) acrylic acid ester copolymer emulsion has been proposed as an emulsion suitable as a pressure-sensitive adhesive (for example, JP-A-53-73235 and JP-A-54-61284,
See JP-A-55-142013. ). In particular, the ethylene-vinyl ester- (meth) acrylic acid ester copolymer emulsion has excellent adhesiveness to a polyolefin substrate. However, for wider application as a pressure-sensitive adhesive, the ethylene-vinyl ester- (meth) acrylic acid ester type copolymer emulsion produced by the conventional method has a holding power when used alone, especially at high temperature. (Heat-resistant creep) and low temperature adhesion were problems.

[0003]

In view of the current situation, the problem to be solved by the present invention is to provide a method for producing an aqueous emulsion most suitable for obtaining a pressure-sensitive adhesive having high adhesive strength, holding power and adhesive strength. That is, ethylene-vinyl ester- (copolymerized with a copolymerizable olefinically unsaturated monomer having a functional group such as a carboxyl group, an amide group or an N-methylol group, which has excellent adhesive properties and can be used alone. A method for producing a (meth) acrylic acid ester-based copolymer emulsion, which is extremely advantageous in industrial practice, and a pressure-sensitive adhesive containing an aqueous emulsion as a main component obtained by the production method.

[0004]

That is, one invention of the present invention is as follows: (A) 5 to 30% by weight, (B) 20 to
85% by weight, 10 to 75% by weight of (C) and 0.3 to 8 parts by weight of the following (D) per 100 parts by weight of the total amount of (B) and (C) subjected to polymerization. A method for producing an aqueous emulsion containing coalescence, in which 10 to 50% of the total amount to be charged (B) and (C) are charged into the polymerization system, the charging of (D) is started, and the total amount of ( The amount of (D) charged at the time of charging B) and (C) is 50 to 90% of the total amount to be charged of (D), and then the remaining amount of (D) is charged to complete the polymerization. It relates to a manufacturing method. (A) Ethylene (B) α, β-Unsaturated carboxylic acid ester represented by the following (Formula 1) (C) Vinyl ester represented by the following (Formula 2) (D) Carboxyl group, amide group, N- Methylol group,
Copolymerizable olefinically unsaturated monomer having epoxy group or hydroxy group

[0005]

[Chemical 1]

(R ₁ represents hydrogen or a methyl group, R ₂ represents an alkyl group having 1 to 18 carbon atoms, and R _{3 to} R ₅ represent
Each independently represents hydrogen or an alkyl group. However, the total number of carbon atoms of R _{3 to} R ₅ is 18 or less. )

Another aspect of the present invention relates to a pressure-sensitive adhesive containing the above aqueous emulsion as a main component.

The details will be described below. Ethylene is contained in the copolymer of the present invention. The content of ethylene in the copolymer is 5 to 30% by weight. If the content is too small, the (normal) adhesive strength, particularly the adhesive strength to the non-polar polymer adherend and the curved surface adhesive strength, will be poor, while if the content is too large, the adhesive strength and holding power will be poor.

Examples of the (B) α, β-unsaturated carboxylic acid ester represented by the above (formula 1) contained in the copolymer of the present invention include methyl acrylate, ethyl acrylate, propyl acrylate, Butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, Examples thereof include butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, lauryl methacrylate, stearyl methacrylate and the like. In particular, the carbon number of R ₂ in (Formula 1) is 4 to 12
Are preferred. As (B), one type of α, β-unsaturated carboxylic acid ester represented by (Formula 1) may be used alone, or two or more types may be mixed and used.

The content of (B) in the copolymer is 20 to 8
It is 5% by weight, preferably 25 to 70% by weight. If the content is too small, the adhesive strength will be poor, and if the content is too large, the adhesive strength to the non-polar polymer adherend will be poor. The α, β-unsaturated carboxylic acid diester can be used in combination for improving the adhesive strength without impairing the original performance as a pressure-sensitive adhesive. Preferable examples include maleic acid diester and fumaric acid diester.

Examples of the vinyl ester (C) represented by the above (formula 2) contained in the copolymer of the present invention include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl laurate and versatic. Examples thereof include vinyl acetate, and vinyl acetate and a combination of vinyl acetate and higher fatty acid vinyl are preferable. In addition,
As (C), one type of vinyl ester represented by (Formula 2) may be used alone, or two or more types may be mixed and used.

The content of (C) in the copolymer is 10 to 7
It is 5% by weight, preferably 20 to 65% by weight. When the content is too small (normal state), the adhesive strength and holding power are poor, while when the content is too large, the adhesive strength is poor.

The copolymerizable olefinic unsaturated monomer (D) having a carboxyl group, an amide group, an N-methylol group, an epoxy group or a hydroxy group contained in the copolymer of the present invention is, for example, acrylic acid, Methacrylic acid, crotonic acid, itaconic acid (including half-ester),
Carboxyl group-containing monomers such as maleic acid (including half ester) and anhydrides thereof; N-such as N-methylolacrylamide and N-butoxymethylacrylamide
Methylol derivative monomer; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxy group-containing monomer such as mono (meth) acrylate of polyhydric alcohol and monoallyl ether of polyhydric alcohol; dimethylaminoethyl methacrylate Amino group-containing monomers such as dimethylaminopropyl acrylamide; epoxy group-containing monomers such as glycidyl (meth) acrylate; amide group-containing monomers such as acrylamide, methacrylamide, and maleinamide.

The content of (D) in the copolymer is 0.3 to 8 parts by weight, preferably 0.5 to 6 parts by weight per 100 parts by weight of the total amount of (B) and (C) used for the polymerization. % By weight. If the content is too small, the holding power and low temperature adhesiveness will be poor, whereas if the content is too large, gelation will occur during polymerization.

The copolymer of the present invention comprises the above (A) to
In addition to (D), (E) a copolymerizable crosslinkable monomer having two or more polymerizable double bonds may be contained. Examples of the monomer include diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol diacrylate, allyl methacrylate, adipic acid diacrylate, trimethylolpropane dimethacrylate, and the like. The content of (E) in the copolymer is usually 5% by weight or less, preferably 3% by weight or less. By using (E) in such a range, the crosslinkability of the emulsion can be improved without impairing the original properties of the pressure-sensitive adhesive.

In the production method of the present invention, the method of charging each polymerization component into the polymerization system is particularly important. That is,
10 to 50% of the total amount to be charged, preferably 10 to 45
% Of (B) and (C) was charged into the polymerization system, the charging of (D) was started, and the total amount of (B) and (C) to be charged was (D) 50 to 90% of the total amount of D) to be charged, preferably 6
It is 0 to 85%, after which it is necessary to charge the remaining amount of (D) to complete the polymerization. When (B) and (C) at the start of preparation of (D) are too small, the ratio (the ratio of (B) and (C) actually charged to the total amount of (B) and (C) to be charged) is too small. Inferior in adhesion and holding power,
On the other hand, if the charging rate is too large, the holding power will be poor. In addition, when the charging rate of (D) (the ratio of (D) actually charged to the total amount of (D) to be charged) at the time of charging all the amounts (B) and (C) is too small, the holding power is poor. On the other hand, if the charging rate is too large, the adhesive strength will be reduced.

The features of the method for producing an aqueous emulsion of the present invention are as described above, but specific examples of other conditions are as follows. The polymerization is carried out by emulsion polymerization, and a radical polymerization initiator, a pH adjuster, a polymerization chain transfer agent and the like usually used in emulsion polymerization can be used. The polymerization pressure is 5 to 200 kg / cm ² of ethylene, and the polymerization temperature is usually 30 to
A range of 70 ° C is suitable. The radical polymerization initiator is a water-soluble radical initiator used in ordinary emulsion polymerization, for example, hydrogen peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, tert-butyl hydroperoxide, etc. alone or L- , D-ascorbic acid, sulfite, rongalit, ferrous sulfate in combination with a reducing agent such as a redox system. pH
Examples of the regulator include acids such as hydrochloric acid, phosphoric acid, acetic acid, succinic acid, carbonic acid and salts thereof; bases such as alkali metal hydroxides, aqueous ammonia and amines. A mercaptan or the like can be used as the chain transfer agent.

In the production method of the present invention, a nonionic surfactant and an anionic surfactant can be used as the emulsion stabilizer during polymerization. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene / polyoxypropylene block copolymers, polyoxyethylene fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Examples of the anionic surfactant include alkyl sulfate ester salts, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phosphates and the like. it can.

In the present invention, a protective colloid may be used in addition to the above nonionic surfactant and anionic surfactant. As the protective colloid, for example,
Partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol,
Polyvinyl alcohols such as carboxyl modified polyvinyl alcohol and silanol group modified polyvinyl alcohol; hydroxyethyl cellulose, methyl cellulose,
Examples thereof include cellulose derivatives such as carboxymethyl cellulose.

Further, a copolymerizable olefinically unsaturated monomer having a sulfonic acid group can be used as a polymerization stabilizer, and sodium vinyl sulfonate, sodium methallyl sulfonate, 2-acrylamido-2-methylpropane sulfonic acid can be used. I can give you soda.

The pressure-sensitive adhesive of the present invention contains the aqueous emulsion obtained by the above-mentioned production method as a main component, and the content thereof is usually 30 to 70% by weight (based on solid content), preferably. It is 40 to 65% by weight. It is also possible to blend and use an acrylic ester emulsion. At the stage of using the aqueous emulsion as a pressure-sensitive adhesive, an antifoaming agent, a viscosity modifier, a filler, etc. may be added as long as the original characteristics are not impaired.

The pressure-sensitive adhesive of the present invention has excellent adhesive strength, holding power and adhesive strength, and can be widely applied to adhesive tapes, adhesive sheets, adhesive labels and the like. These products are those that have good pressure-sensitive adhesive properties balanced by applying the emulsion of the present invention to substrate materials such as plastic films, papers, metal foils, etc. using conventional and known equipment and methods. can get. Particularly, it has excellent adhesive force, adhesive force and holding power even for non-polar adherends such as polyolefin.
Further, since it has excellent holding power, there is no drawback that the adhesive will come out when it is stored for a long period of time.

[0023]

EXAMPLES The present invention will now be described with reference to examples, but the present invention is not limited thereto. Example 1 In a pressure-resistant autoclave equipped with an anchor type stirrer, 1300 parts by weight of deionized water, 54.4 parts by weight of an emulsion stabilizer, and 1 part of acetic acid.
An aqueous solution containing 1 part by weight, 5 parts by weight of sodium acetate, and 10 parts by weight of Rongalit was charged, and the system was replaced with nitrogen and then with ethylene under stirring. Next, set the system temperature to 50 ° C.
To 680 parts by weight of vinyl acetate as the component (C), 408 parts by weight of 2-ethylhexyl acrylate as the component (B), and 450 parts by weight of a 6.25% by weight aqueous ammonium persulfate solution. At the same time, it was charged at a constant rate for 4 hours. During this period, the reaction temperature was adjusted to 50 ° C. and the ethylene pressure was kept at 60 k during polymerization.
It was maintained at g / cm ² and 1 hour and 48 minutes after the start of addition of the mixed monomer (at the time when 45% of the total amount of the mixed monomer to be charged was charged), 0.5% by weight of N- as the component (D).
Start adding 70 parts by weight of methylol acrylamide,
When the total amount of the mixed monomer was charged (after 4 hours), the charged amount was adjusted to 85% of the total amount. Then, after charging the remaining amount, aging was further performed at 50 ° C. for 1 hour. The aqueous emulsion thus obtained has a solid content of 45% by weight.
Met. The emulsion was uniformly applied to a release paper having a thickness of 110 μm using an automatic coating device so that the pressure-sensitive adhesive application thickness would be 25 μm (after drying), and then dried with warm air at 80 ° C. for 5 minutes, Further, the pressure-sensitive adhesive sheet was obtained by transferring to 55 g / m ² of high-quality adhesive sheet. The obtained pressure-sensitive adhesive sheet was evaluated by the following methods. The results are shown in Table 2.

(1) Adhesive Strength (Normal Adhesive Strength) A stainless steel plate (SUS304), a polyethylene (PE) plate and a polypropylene (PPr) plate, which are well polished with a water-resistant abrasive paper of No. 280 according to JIS R-6253, are attached to JIS.
The sample crimped by an automatic crimping device according to the method of Z-238 is subjected to 180 ° C. under the conditions of 23 ° C. and 65% RH (relative humidity).
The strength (unit: g / 25 mm) at the time of peeling at a rate of 300 mm / min in the direction of the angle was measured by a Tensilon tensile tester and used as the (normal state) adhesive force to each adherend.

(2) Adhesive strength (tack test) DOW method (Proc. Inst. Rubber I
nd. 1105 (1954)), 23 ° C, 65%
Under the condition of RH, a 10 cm long adhesive sheet was attached to the slope on a stainless plate with an inclination angle of 30 degrees, and the upper part of the slope 10
From the position of cm, 32 kinds of stainless steel balls with a diameter of 1/32 inch to 1 inch are rolled at an initial speed of 0 and the size of the ball with the maximum diameter (ball No.) that stops on the adhesive sheet. is there. No. The larger the value, the better the adhesive strength.

(3) Holding power (cohesive force) A test piece was attached to a stainless steel plate (SUS 304), which was well polished with water-resistant abrasive paper No. 280 according to JIS R-6253, so that the adhesive area of the test piece was 25 × 25 mm. 2k
The sample was pressed back and forth once with a rubber roller of g, and the pressed sample was subjected to a static load of 1 kg in an atmosphere of 40 ° C., and the time when the load dropped was shown. The longer the time, the better the cohesive strength.

(4) Low-temperature adhesive strength The pressure-sensitive adhesive sheet thus obtained was pressure-bonded to the PE plate shown in (1) according to the method of JISZ-238 under the condition of -30 ° C, and under the condition of -30 ° C ( The strength obtained by the measuring method shown in 1) was taken as the low temperature adhesive strength.

(5) Adhesive strength on curved surface A polyethylene rod having a diameter of 1 cm was attached with 1.0 cm × 2.
5cm test piece is pasted, 105 ℃ × 8Hr, 0 ℃ × 1
After leaving it under the condition of 6 Hr for 2 cycles,
It evaluated by the following criteria. When there is no abnormal appearance ○ When the tip is floating △ When it is completely peeled off ×

Examples 2 to 6 and Comparative Examples 1 to 6 The same procedure as in Example 1 was carried out except that the conditions shown in Tables 1 and 3 were used. The results are shown in Tables 2 and 4.

The results show the following. In all the examples satisfying the conditions of the present invention, the results to be satisfied are shown in all the evaluation items. On the other hand, each comparative example lacking the definition of the present invention shows unsatisfactory results as follows. Comparative Example 1 which does not use the component (D) is inferior in holding power and low-temperature adhesiveness. In Comparative Example 2 in which the component (D) was excessive, gelation occurred during polymerization. Comparative Example 3 in which the component (B) was not used is inferior in adhesive strength and low temperature adhesive strength. Comparative example 4, (B) and (C) in which the start time of charging of (D) was inappropriate
Comparative Example 5 in which the charging completion time was unsuitable, and Comparative Example 6 in which any of the time points were unsuitable had poor holding power.

[0031]

[Table 1] ---------------------------- * 1 (A) 20 20 8 15 10 10 (B) 30 40 65 45 63 63 (C) 50 40 25 35 27 27 (D) Type N-MAM AM 2HEA GMA N-MAM N-MAM amount 0.5 2.0 5.0 1.0 1.0 3.0 Preparation method * 2 (D) Start time 45 45 10 30 15 15 (B) + (C) Completion time 85 85 80 70 65 85 Evaluation Adhesive force g / 25cm PE 1300 1180 960 1060 1030 1000 PPr 1520 1570 1010 1270 1140 1030 SUS 1670 1530 1190 1590 1250 1200 Adhesive force Ball No. 15 13 18 16 18 19 Holding force min 870 1160 ＞ 810 ＞ 1440 960 ＞ 1440 Low temperature adhesive force g / 25cm 40 20 40 30 50 40 Curved adhesive force ○ ○ ○ ○ ○ ○ −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0032]

[Table 2] ------------------ Comparison composition 1 2 3 4 5 6 Copolymer composition * 1 (A) 20 20 30 10 10 10 (B) 40 40 10 63 63 63 (C) 40 40 60 27 27 27 (D) Type-N-MAM AM N-MAM N-MAM N-MAM amount 0 15.0 1.0 1.0 1.0 1.0 Preparation method * 2 (D) Start time-15 15 0 30 0 (B) + (C) Completion time-80 80 85 100 100 Evaluation Adhesive force g / 25cm PE 830 Weight 800 910 1020 860 PPr 860 840 950 1420 930 SUS 970 900 940 1320 1410 Adhesive force Ball No. 10 Ge 4 19 17 17 Holding force min 70 Le ＞ 610 200 310 160 Low temperature adhesive force g / 25cm 0 0 0 0 30 80 Curved adhesive force ○ ○ ○ ○ ○ −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

* 1 Copolymer composition Numbers in the table (A) to (C):% by weight in the copolymer (D): Total amount of (B) and (C) used for polymerization 1
Parts by weight per 00 parts by weight Meaning of symbols (A): Ethylene (B): 2-Ethylhexyl acrylate (C): Vinyl acetate (D): N-MAM; N-methylol acrylamide AM; Acrylamide 2HEA; 2- Hydroxyethyl acrylate GMA; glycidyl methacrylate

* 2 Method of charging (D) Start time: Charge ratio of (B) and (C) at the time when the charge of (D) was started (actual charge for all amount of (B) and (C) to be charged) (B) and (C)
%) (B) + (C) Completion point: (B) of the total amount to be charged and the charging rate of (D) at the time of charging (C) (Actual charging to the total amount of (D) to be charged (D) ) Ratio)

[0035]

As described above, according to the present invention, a method for producing an aqueous emulsion most suitable for obtaining a pressure-sensitive adhesive having high adhesive strength, holding power and tackiness, which is extremely advantageous in industrial practice. It was possible to provide a production method and a pressure-sensitive adhesive containing an aqueous emulsion obtained by the production method as a main component.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08F 220/28 MMM C09J 131/02 PFV 133/06 JDE

Claims (2)

[Claims] 1. The following (A) 5 to 30% by weight, (B) 20
-85% by weight, (C) 10-75% by weight, and 0.3 to 8 parts by weight of the following (D) per 100 parts by weight of the total amount of (B) and (C) used for polymerization. A method for producing an aqueous emulsion containing a polymer, wherein the charging of (D) is started when 10 to 50% (B) and (C) of the total amount to be charged are charged into the polymerization system, and The amount of (D) charged at the time of charging (B) and (C) is 50 to 90% of the total amount to be charged of (D), and then the remaining amount of (D) is charged to complete the polymerization. Manufacturing method. (A) Ethylene (B) α, β-Unsaturated carboxylic acid ester represented by the following (Formula 1) (C) Vinyl ester represented by the following (Formula 2) (D) Carboxyl group, amide group, N- Methylol group,
Copolymerizable olefinically unsaturated monomer having epoxy group or hydroxy group (R ₁ represents hydrogen or a methyl group, R ₂ has 1 to 1 carbon atoms.
8 represents an alkyl group, and R _{3 to} R ₅ each independently represent hydrogen or an alkyl group. However, R _{3 to} R ₅
Has a total carbon number of 18 or less. ) 2. A pressure-sensitive adhesive containing the aqueous emulsion according to claim 1 as a main component.