JPS59210917A - Production of polychloroprene latex - Google Patents

Abstract

PURPOSE:To produce the titled latex having a large initial tack and good stability, by polymerizing chloroprene in an emulsion of a copolymer having a specified glass transition point. CONSTITUTION:An emulsion of a copolymer having a glass transition point <=(T -10 deg.C) is formed by emulsion-polymerizing a monomer mixture comprising (a) 1-30wt% polymerizable unsaturated carboxylic acid (e.g., acrylic or itaconic acid), (b) 0.01-30wt% water-soluble monomer (e.g., methyl acrylate), (c) 5- 70wt% monomer capable of forming a flexible component (which can form a homopolymer of a glass transition point <=0 deg.C), e.g., lauryl methacrylate, and (d) 5-70wt% monomer capable of forming a rigid component (which can form a homopolymer of a glass transition point >=0 deg.C), e.g., styrene. 99-30pts.wt. chloroprene is added to 1-70pts.wt. (in terms of the above monomer mixture) above produced copolymer emulsion, and the mixture is polymerized at a temperature T.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polychloroprene latex which has excellent stability and exhibits high initial adhesive strength when used as an adhesive.

Chloroprene polymers are widely used in adhesives in the form of either solutions dissolved in organic solvents or latex systems using water as a medium. However, a disadvantage of latex-based adhesives is that their initial adhesive strength is lower than that of solution-based adhesives. As a result of intensive research to improve this drawback, the present invention has been achieved.

That is, the present invention provides polymerizable unsaturated carboxylic acids 1 to 60
Weight: 0.01 to 60% by weight of a water-soluble monomer, 5 to 90% by weight of a monomer that provides a soft component with a homopolymer glass transition temperature of 0°C or less, and the glass transition temperature of the homopolymer. Monomer 5 to provide a hard component with a temperature of 0°C or higher
The glass transition temperature of the copolymer obtained by copolymerizing a 100% monomer mixture in the entire composition from 70-fold IJ is (T-
10) °C or less, preferably (T-/)0) to (T-2
from 1 to 70 parts by weight of a monomer mixture selected to be at 0) °C (where T indicates the polymerization temperature in degrees Celsius during the polymerization of chloroprene) to 99 parts by weight of chloroprene 6D. A method for producing polychloroprene latex, which is characterized by adding and polymerizing polychloroprene latex, which has excellent stability and exhibits high initial adhesive strength when used as a single adhesive.

The production of the polychloroprene latex of the present invention is carried out in two stages. Each stage of polymerization can be carried out separately or sequentially.

The polymerizable unsaturated carboxylic acids used in the first step include acrylic acid, methacrylic acid, maleic acid, fumaric acid,
Examples include itaconic acid. These monomers are used to maintain the stability of the latex and are used in amounts ranging from 1 to 60% by weight of the monomer mixture used in the first stage.

If it is less than 1% by weight, the stability of the latex will be poor, and if it exceeds 60% by weight, the amount of precipitates during polymerization will increase.

Similarly, the water-soluble monomer used in the first step may be any monomer having a solubility in 100 parts of water of 19 or more at 20°C, excluding the above-mentioned polymerizable unsaturated carboxylic acids, such as acrylic acid. Methyl, acrylonitrile, vinyl acetate.

Examples include sodium styrene sulfonate and acrylamide. The polymerizable unsaturated carboxylic acids of these seven substances are soluble in water, while the seven substances that provide the soft and hard components described below are poorly soluble or insoluble in water. Used to enhance copolymerizability. Although it is known that a stable latex can be obtained using a polymerizable unsaturated carboxylic acid, its stability has been insufficient due to poor copolymerizability with other water-soluble or insoluble monomers.

The present inventors have discovered that a water-soluble monomer can be used to enhance this copolymerizability. This water-soluble monomer is
It is thought that copolymerizability with water-soluble polymerizable unsaturated carboxylic acids is enhanced because it is compatible with monomers that are sparingly soluble or insoluble in water.

The water-soluble monomer is used in an amount of 0.01 to 60% by weight of the monomer mixture used in the first stage, but 0.01
If it is less than 60% by weight, the stability of the latex will be poor, and if it exceeds 60% by weight, the viscosity of the latex will be extremely high.

Furthermore, in the first step, monomers providing the soft component and the hard component are copolymerized. These form the core of the emulsion particles that are copolymerized in the first stage.

As described below, the glass transition temperature (hereinafter Tg
The Tg of the homopolymer is such that the temperature (hereinafter referred to as T) is below (T-10)" 0
Tg of monomers and homopolymers that provide soft components below ℃
A monomer that provides a hard component with a temperature of 0°C or higher is used in combination. Monomers providing soft components include hexyl methacrylate (-5°C) and lauryl methacrylate (-65°C).
°C).

Examples include butyl acrylate (-55°C) and 2-ethylhexyl acrylate (-60°C).

Monomers that provide hard components include methyl methacrylate (105°C) and ethyl methacrylate (55°C).
, vinyl chloride (81°C), styrene (100°C), etc. In addition, the Tg of the heptad homopolymer is shown within 0.

The above monomers are copolymerized in the first step, and the Tg of the copolymer in this first step is (T-10) "C or less, preferably (T-6o) to (T-20)" C. The monomer components are removed. As the polymerization temperature of chloroprene decreases, the crystallinity of polychloroprene itself increases. Therefore, when the polymerization temperature of chloroprene is lowered, the polychloroprene eyes become harder. Therefore, in this case, the most suitable copolymer for the first stage is softer, that is, the one with a lower Tg, the more clever the result will be. Therefore, the Tg of the copolymer in the first stage of the present invention depends on the polymerization temperature T ("C)" of chloroprene, and in order to obtain high initial adhesion, "(T-1o)" (hereinafter referred to as preferable Shikuke (T
-60) to (T-20)"C. If the Tg of the copolymer is (T-10) or higher, the particle surface will be too hard and the cohesive force will be poor. , the initial adhesive strength decreases and the effects of the present invention cannot be obtained.

Here, the Tg of the copolymer in the present invention is It [written by Nielsen, translated by Nobuharu Onogi [Mechanical Properties of Polymers 126
It was calculated using the method described in 7f12 on page 27.

The polymerization temperature in the first stage is not particularly limited, and can be freely selected from 0°C to 100°C depending on the catalyst system used, but preferably from 50 to 80°C. Although the polymerization time varies depending on the polymerization conditions and is not specified, it is preferable to carry out the polymerization until the polymerization is essentially complete.

Although not necessarily required in the first stage polymerization, for the purpose of further improving the stability of the tube metal, emulsifiers used in ordinary emulsion polymerization, such as argyl sulfates, alkylbensene sulfonates, fatty acid salts, Polyoxyethylene alkyl ether, etc., with respect to water, its 0 to 1 weight K"f
There is no problem in using it for a small amount of h', on the order of %. Additionally, alkyl mercaptan may be controlled in the system.

Polymerization initiators used in the present invention include, for example, persulfates,
Any initiator used for radical polymerization, such as alkylhydroperoxide, may be used; in particular, potassium persulfate and ammonium persulfate initiators with persulfate ions are extremely effective.These initiators further stabilize latex particles. also contributes. However, these can be used alone or in combination with reducing substances such as thiosulfates, thiosulfites, and specific amines.

In the present invention, as a second step, chloroprene is added to the emulsion produced as described above, and the polymerization of chloroprene is continued to obtain polychloroprene latex. At this time, by adding a base to the emulsion, the pH of the emulsion is adjusted to 7 or higher, preferably 9.
It is effective to set the value to 11. This is because the carboxyl groups on the surface of the emulsion particles are ionized and have anions on the surface of the particles, which can further increase the stability of the latex. Examples of the base used in this case include sodium hydroxide, potassium hydroxide, and aqueous ammonia.

In the polymerization of chloroprene, chloroprene can be added either all at once or continuously.

When adding chloroprene continuously, the time for adding chloroprene can be freely selected, but it is desirable to prevent a large amount of monomer oil droplets from appearing in the polymerization system, and it is preferable to add chloroprene over 100 minutes or more. The polymerization temperature of chloroprene can be set in the range of 0 to 60°C as in the case of ordinary emulsion polymerization of chloroprene.

The polymerization of chloroprene may be carried out until all the monomers are substantially polymerized, but in order to develop better initial adhesive strength, the polymerization conversion should be 40 to 85%, preferably 60 to 80%. When this is reached, it is desirable to add a commonly used polymerization terminator to stop the polymerization. In this case, the remaining monomer can be removed by a conventional method to obtain a latex. When the polymerization conversion rate is less than 40 fv, adhesive strength is low and productivity is also poor. On the other hand, if it exceeds 85%, chloroprene will gel and the initial adhesive strength will decrease.

In the polymerization of chloroprene, the molecular weight is controlled by adding a chain transfer agent such as an alkyl mercaptan to chloroprene, as is done in the production of ordinary chloroglene polymers. Furthermore, other vinyl monomers copolymerizable with chloroprene, such as methacrylic branched esters, acrylic acid esters, styrene, etc., diene monomers, such as butadiene, isoprene, 2,6-dichlorobutadiene, etc., or crosslinking monomers, such as Polychloroprene latex can be modified by adding a small amount of divinylbenzene, ethylene glycol dimethacrylate, etc. of 20 or less weights and copolymerizing it with chloroprene. Such modification is not particularly limited as long as it does not impair the essence of the present invention.

The amount of chloroprene added and polymerized in the second stage is 1 to 70 parts by weight of the monomer mixture used in the first stage.
99-30 parts by weight are used. If it exceeds 4 parts of 99:flj'b, the stability of the latex will be poor and precipitates will be generated during polymerization. If the amount is less than 30 parts by weight, the properties as a polychloroprene latex will be lacking. In addition, the solid content concentration of the polychloroprene latex that is finally produced is the same as that of the latex produced by ordinary emulsion polymerization.
~70% by weight.

The polychloroprene latex thus obtained is essentially free of emulsifiers, exhibits excellent adhesive stability, and has high initial adhesive strength, and has many properties similar to conventional polychloroprene latex. It can be used for various purposes. At that time, like traditional polychloroprene latex, vulcanizing agents are used.

Various types of anti-aging agents, thickeners, tackifiers, etc. can also be added.

In particular, the polychloroprene latex of the present invention has carboxyl groups on the particle surface, and when mixed with polyfunctional metals such as diols, diebodies, and isocyanates,
By forming a crosslinked structure, various adhesive properties such as strength and water resistance can be improved.

Furthermore, when resins conventionally known as adhesion promoting resins, such as rosin-based resins, rosin derivatives, and terpene-based resins, are blended, the tackiness can be further improved than when blended with conventional polychloroprene latex. This makes it possible to further increase the high initial adhesive strength that is characteristic of the polychloroprene latex of the present invention.

In order to make the present invention easier to understand, the present invention will be explained below using some examples, but the present invention is not limited to these examples. In the text, parts refer to parts by weight unless otherwise specified.

The initial adhesive strength was measured using No. 9 canvas 2 cut to 25 mm diameter.
Apply latex to each sheet, repeat drying at 80°C (10 minutes), and after the third application, leave to dry for the specified oven time (120 minutes except for Example 18), then paste together, 90- Immediately after crimping with a roller 5 times, the peel strength was determined using an Instone tensile tester and used as the initial adhesive strength.

The adhesive strength was measured in the same way as before, after the 6th application on the canvas, the sheets were pasted together in an oven time of 60 minutes, and 5 kg was applied.
After crimping 5 times with an o-ler, leave it at 25°C for 1 day,
Dry for 1 hour at °C. After leaving it for another day at 25°C,
The peel strength was determined. Further, a test piece prepared in the same manner was immersed in warm water at 50°C for 24 hours, and then the peeling strength was measured to evaluate water resistance.

Explanation of symbols used below VAc Vinyl acetate MA Methyl acrylate AAm Acrylamide Mass Sodium styrene sulfonate St
Styrene λ4MA Methyl methacrylate BA n-Butyl acrylate Examples 1 to 4 In a nitrogen gas stream, 400 parts of water in which 0.4 part of IJium was dissolved was charged into a polymerization container and heated to 70°C. After that, 5 parts of ammonium persulfate was added, followed by 24 parts of styrene, 24 parts of methyl methacrylate, 57 parts of n-butyl acrylate, 5.4 parts of acrylic acid, 2 parts of n-octyl mercaptan [2 parts of Li, and 2 parts of heptamine shown in Table 1]. Polymerization was carried out while dropping a monomer mixture consisting of 1.5 ml of monomer mixture over 120 minutes. After the dropwise addition was completed, stirring was continued at 70°C for 1 hour to complete the polymerization. At this time, substantially no coagulum was observed in any case, and the stability of the emulsion was excellent.

Furthermore, chloroprene was subsequently polymerized.

First, the temperature of the emulsion obtained above was lowered to 40°C, and then 10 f(t%) sodium hydroxide aqueous solution was added to adjust pII to 1α0.Next, 64 parts of n-octylmercaptan CL was added. Polymerization was carried out while dropping 320 parts of chloroprene over 100 minutes.The temperature was maintained at 40°C even after the completion of the i'r reaction, and the polymerization was carried out at a temperature where substantially all of the chloroprene had been polymerized. Substantially no generation of substances was observed, the solid content of the obtained latex was 50% by weight, and the stability of the latex was also excellent.Furthermore, when the initial adhesive strength was measured, as shown in Table 1, it was found that the present invention All products were superior to commercially available polychloroprene latex.

Examples 5 to 8 and Comparative Example 1 In a nitrogen gas stream, 400 parts of water in which 70.4 parts of sodium lauryl sulfate was dissolved was charged into a polymerization container, heated to 70°C, and then 3 parts of ammonium persulfate was added. Subsequently, a monomer mixture consisting of the monomers having the composition shown in Table 2 (expressed in parts by weight used), 3 parts of vinyl acetate, 5.4 parts of acrylic acid, and 015 parts of n-octyl mercaptan was added dropwise over 120 minutes for polymerization. . 1 at 70°C after the completion of dropping.
Stirring was continued for an hour to complete the polymerization. At this time, substantially no coagulum was observed in any case, and the stability of the emulsion was excellent.

Next, chloroprene was polymerized in the same manner as in Example 1. At this time, substantially no coagulation was observed in any case, and the stability of the latex was excellent. Further initial contact';
When the II strength was measured, as shown in Table 2, the superiority of the product of the present invention was clear.

Table 1 Table 2 Example 9 A copolymer emulsion with the same composition as that used in Example 1 was synthesized, and then the temperature of the emulsion was lowered to 40°C, and then a 10% by weight aqueous sodium hydroxide solution was added. death,
The pH was set to 10.2. Next, 450 parts of chloroprene to which 9 parts of n-octylmercaptan α had been added was added dropwise over 100 minutes for polymerization. After completion of the dropwise addition, the temperature was maintained at 40°C, and when the polymerization conversion rate of chloroprene reached 70%, 01 part of phenothiazine was added to stop the polymerization. continuation,
Unreacted chloroprene was removed by stripping, and a polychloroprene latex with a solid content of 45 wt.
I was. At this time, no coagulum was observed, and the stability of the latex was excellent. Furthermore, compared to Example 1, the initial adhesive strength increased by 10kg725. Got latex. At this time, a latex with a solid content of 44% by weight was obtained, but no coagulum was generated and the stability was excellent. The initial adhesive strength showed values of 75 and 9725+n.

Examples 11 to 16 and Comparative Example 2.5 First-stage emulsions were synthesized in the same manner as in Example 5 using the monomer compositions shown in Table 3 (expressed in parts by weight used). Next, polymerization of chloroprene was carried out in the same manner as in Example 9 except that the temperature was changed to 15°C to obtain a latex. At this time, substantially no coagulation was observed in any case, and the stability of the latex was excellent. Furthermore, the initial adhesive strength showed excellent values in the Tg range different from Examples 5 to 8.

Table 3 Example 14 Using Examples 9 and 10 and commercially available polychloroprene latex, for 100 parts of polymer in the latex,
An adhesive composition was prepared by blending 5 parts of zinc white, 5 parts of ethylene glycol, and 30 parts of a rosin resin as a tackifying resin.

The adhesive properties are shown in Table 4, and the product of the present invention has a high initial adhesive strength, and even if the oven time is changed, a high initial adhesive strength is always obtained, and the adhesive strength develops quickly.
Still in use] It had excellent performance as a water-based contact adhesive with a long shelf life. Furthermore, the water resistance after adhesion was also excellent.

Table 4

Claims (1)

[Claims] (1) 1 to 60% by weight of polymerizable unsaturated carboxylic acid. Water-soluble heptamine 0.01 to 30% by weight, homopolymer glass transition temperature of 5 to 90% by weight, which provides a soft component with a homopolymer glass transition temperature of 0°C or less, and the glass transition temperature of the homopolymer. Monomer 5 to 70 that provides a hard component with a temperature of 0°C or higher
The glass transition temperature of the copolymer obtained by copolymerizing a monomer mixture consisting of Monomer mixtures 1-7 selected to be
5 parts by weight of chloroprene in the copolymer emulsion
A method for producing polychloropre/latex, which comprises adding 0 to 99 parts by weight and polymerizing it.