JP2013203820A - Acetoacetyl-modified chloroprene rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acetoacetyl-modified chloroprene rubber with excellent layer separation resistance, and an adhesive using the same.SOLUTION: An acetoacetyl-modified chloroprene rubber is obtained by copolymerizing 0.5 to 10 pts.mass of an acetoacetylated monomer based on 100 pts.mass of the total monomers. The acetoacetylated monomer used for the acetoacetyl-modified chloroprene rubber is preferably at least one selected from allyl acetoacetate, vinyl acetoacetate, 2-acetoacetoxyethyl acrylate, 2-acetoacetoxyethyl methacrylate, 2-acetoacetoxypropyl acrylate, and 2-acetoacetoxypropyl methacrylate.

Description

The present invention relates to an acetoacetyl-modified chloroprene rubber, a method for producing the same, and an adhesive using the acetoacetyl-modified chloroprene rubber.

Chloroprene rubber is used in various applications because of its excellent heat resistance, weather resistance, ozone resistance, chemical resistance, flame retardancy, and the like.
A solvent-type adhesive is one of the representative examples, and is used in various applications because of its wide adaptability to adherend and good balance of adhesive properties. In recent years, organic solvents used in solvent-based adhesives are desired to be converted from aromatic ones such as toluene, xylene, and ethylbenzene, which cause sick house syndrome, to non-aromatic ones. However, with this conversion, so-called layer separation that separates into a component that dissolves in an organic solvent and an insoluble component tends to occur when the solvent-based adhesive is stored.

As means for improving the layer separation of the solvent-type adhesive, (1) a method of extracting and removing rosin as an emulsifier from a rubber chip (see, for example, Patent Document 1), and (2) coexisting ethylenically unsaturated carboxylic acid. A method of blending a polymerized chloroprene copolymer latex and a chloroprene copolymer latex obtained by copolymerizing a copolymerizable monomer other than an ethylenically unsaturated carboxylic acid (for example, see Patent Document 2) is known. ing.

US Pat. No. 3,427,268 JP 2007-332206 A

An object of the present invention is to provide a chloroprene rubber capable of producing a solvent-type adhesive having excellent layer separation resistance and an adhesive using the same.

That is, the present invention is an acetoacetyl-modified chloroprene rubber containing 0.02 to 0.50 mol% of acetoacetyl groups in all polymers. The acetoacetyl-modified chloroprene rubber is preferably obtained by copolymerizing 0.5 to 10 parts by mass of an acetoacetylated monomer with respect to 100 parts by mass of the chloroprene monomer alone or chloroprene monomer and a monomer copolymerizable with the chloroprene monomer. . The acetoacetylated monomer is at least one selected from allyl acetoacetate, vinyl acetoacetate, 2-acetoacetoxyethyl acrylate, 2-acetoacetoxyethyl methacrylate, 2-acetoacetoxypropyl acrylate, 2-acetoacetoxypropyl methacrylate Is preferred.
The Mooney viscosity of the acetoacetyl-modified chloroprene rubber is preferably 30 to 100 ML (1 + 4) 100 ° C.
The acetoacetyl-modified chloroprene rubber is composed of chloroprene monomer alone or 100 parts by mass of a monomer that can be copolymerized with chloroprene monomer and chloroprene monomer, and 0.5 to 10 parts by mass of acetoacetylated monomer. It is produced by an emulsion polymerization reaction in the presence of 0.5 to 7 parts by mass of a salt until the polymerization rate reaches 50% or more. The obtained acetoacetyl-modified chloroprene rubber can be dissolved in an organic solvent to form an adhesive.

ADVANTAGE OF THE INVENTION According to this invention, the chloroprene rubber which can produce the solvent-type adhesive excellent in the layer-separation resistance, and an adhesive using the same are obtained.

The chloroprene monomer is 2-chloro-1,3-butadiene.

A monomer copolymerizable with the chloroprene monomer is added to adjust the mechanical properties of the resulting adhesive. The type is not particularly limited. For example, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, acrylic acid or esters thereof , Methacrylic acid or its esters, sulfur and the like. Two or more of these monomers can be used in combination as required.
When these monomers are copolymerized, it is preferable to copolymerize such that chloroprene monomer is contained in 70 parts by mass or more in 100 parts by mass of all monomers. By adjusting the content of the chloroprene monomer within this range, the initial strength and normal strength of the obtained adhesive can be maintained.

An acetoacetylated monomer is a monomer having an acetoacetyl group in the molecule, and is a compound capable of forming a complex by coordination with a transition metal. The acetoacetylated monomer is copolymerized with a chloroprene monomer to obtain an acetoacetyl-modified chloroprene rubber, and when used as an adhesive, exhibits an effect of improving the layer separation resistance.

Examples of the acetoacetylated monomer include allyl acetoacetate, vinyl acetoacetate, 2-acetoacetoxyethyl acrylate, 2-acetoacetoxyethyl methacrylate, 2-acetoacetoxypropyl acrylate, 2-acetoacetoxypropyl methacrylate, and the like. Among these, 2-acetoacetoxyethyl methacrylate can be preferably used in terms of handling.

The acetoacetyl group content (modified amount) in the acetoacetyl-modified chloroprene rubber is preferably in the range of 0.02 to 0.50 mol% in the entire polymer. If it is less than 0.02 mol%, the effect of improving the layer separation resistance of the obtained acetoacetyl-modified chloroprene rubber cannot be obtained. Moreover, when it contains exceeding 0.50 mol%, an acetoacetyl modified chloroprene rubber will chelate with a metal oxide at the time of adhesive preparation, and will gelatinize. A more preferable range of the content of the structural unit is 0.05 to 0.40 mol%, and more preferably 0.10 to 0.30 mol%.

In order to adjust the amount of acetoacetyl modification in the range of 0.02 to 0.50 mol% in all monomers, some adjustment is necessary depending on the polymerization conditions. For example, acetoacetyl with respect to 100 parts by mass of chloroprene monomer The monomer can be obtained by copolymerizing 0.5 to 10 parts by mass of the monomer.

The copolymerization of the chloroprene monomer and the acetoacetylated monomer may be carried out in the same manner as in the conventionally known polymerization method of chloroprene monomer. For example, these monomers can be obtained by emulsion polymerization by a commonly used method in the presence of a polymerization initiator generally used for polymerization of chloroprene monomers.

As the polymerization initiator, known organic peroxides such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and t-butyl hydroperoxide generally used for emulsion polymerization of chloroprene monomers are used.

The emulsifying / dispersing agent used in the emulsion polymerization is not particularly limited, but the film-like chloroprene rubber at the time of freeze-coagulation drying after the polymerization is given appropriate strength to prevent excessive shrinkage and breakage. It is preferable to use rosin acid or an alkali metal salt thereof because it can be used. Rosin acid is a mixture of resin acid, fatty acid and the like. Resin acids include abietic acid, neoabietic acid, parastrinic acid, pimaric acid, isopimaric acid, dehydroabietic acid, dihydropimaric acid, dihydroisopimaric acid, secodehydroabietic acid, dihydroabietic acid, etc. , Oleic acid, linoleic acid and the like. The composition of these components varies depending on the difference in rosin collection methods classified into gum rosin, wood rosin and tall rosin, pine production area and tree species, distillation purification, and disproportionation (disproportionation) reaction. Not. In view of emulsion stability and ease of handling, use of sodium salt or potassium salt is preferred. The addition amount of the rosinate is not particularly limited, but is preferably 0.5 to 5 parts by mass and more preferably 1 to 4 parts by mass with respect to 100 parts by mass of all monomers. When the amount is less than 0.5 parts by mass, the emulsion stability becomes poor and the polymerization cannot be stably performed. On the other hand, when the amount is more than 5 parts by mass, when the obtained chloroprene rubber is used as a solvent-type adhesive, its water resistance strength and layer separation stability are lowered.

The polymerization temperature and the final conversion rate of the chloroprene monomer are not particularly limited, but the polymerization temperature is preferably 0 to 50 ° C, more preferably 10 to 40 ° C. By setting the polymerization temperature within this range, the water in the reaction solution does not coagulate and the chloroprene monomer does not volatilize.

The molecular weight of chloroprene rubber can be adjusted by the amount of chain transfer agent added. That is, when the addition amount of the chain transfer agent is increased, the molecular weight of the chloroprene rubber can be decreased, and when the addition amount is decreased, the molecular weight can be increased. The chain transfer agent to be used is not particularly limited, and a chain transfer agent generally used for polymerization of chloroprene monomer can be used. Examples of the chain transfer agent include long-chain alkyl mercaptans such as n-dodecyl mercaptan and t-dodecyl mercaptan, dialkylxanthogen disulfides such as diisopropylxanthogen disulfide and diethylxanthogen disulfide, and iodoform.

The amount of chain transfer agent used is not particularly limited, but is selected so that the molecular weight of the chloroprene polymer (or the Mooney viscosity of the chloroprene rubber obtained by isolating the polymer) is appropriate. Although it varies depending on the structure of the alkyl group and the target molecular weight, it is generally used in the range of 0.05 to 5.0 parts by weight, preferably 0.1 to 0.5 parts by weight with respect to 100 parts by weight of the chloroprene monomer.

The final conversion of the chloroprene monomer is preferably carried out so as to fall within the range of 50 to 95% by mass. In order to adjust the final conversion rate, the polymerization may be stopped by adding a polymerization inhibitor that stops the polymerization reaction when the desired conversion rate is reached.

As the polymerization inhibitor, a commonly used inhibitor can be used and is not particularly limited. For example, thiodiphenylamine, 4-tertiarybutylcatechol, 2,2-methylenebis-4-methyl-6-tersia Examples include libutylphenol.

Unreacted chloroprene monomer is removed by, for example, a steam stripping method, and then the pH is adjusted, and acetoacetyl-modified chloroprene rubber is obtained through ordinary freeze-coagulation, water washing, hot air drying and the like.

The acetoacetyl-modified chloroprene rubber can be used as an adhesive by dissolving it in an organic solvent.

Here, as a general method for producing a solvent-type adhesive, after dissolving an alkylphenol resin or magnesium oxide (MgO) in an organic solvent and allowing to stand at 25 ° C. for 20 hours, chloroprene rubber, metal oxide, anti-aging A method of dissolving a mixture obtained by kneading an agent or the like with a roll is known. However, the acetoacetyl-modified chloroprene rubber of the present invention does not need to be kneaded with a roll together with a metal oxide or an antioxidant, and can be directly dissolved and dispersed in an organic solvent to form an adhesive.

The organic solvent used in the adhesive is not an aromatic solvent such as toluene, xylene, or ethylbenzene that causes sick house syndrome, but n-hexane, cyclohexane, methylcyclohexane, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, etc. It is preferable that the chloroprene rubber is dissolved only by a mixture of poor solvents that are non-aromatic and poor in solubility of the chloroprene rubber alone.

The amount of the organic solvent used may be appropriately adjusted depending on the use and type of the adhesive, and is not particularly limited, but when adjusted so that the solid content concentration of the acetoacetyl-modified chloroprene rubber is 10 to 30% by mass, This is preferable because the adhesive has a good balance between heat-resistant adhesive strength and initial adhesive strength.

You may add a metal oxide, tackifying resin, and anti-aging agent to an adhesive agent. By adding these additives to the adhesive, it is possible to improve the initial adhesive strength, normal adhesive strength, spray coatability, and the like of the obtained adhesive.

As the metal oxide, for example, zinc oxide (zinc white), aluminum oxide, titanium oxide, magnesium oxide, or the like can be used. As the tackifier resin, for example, phenol resin, rosin resin, coumarone resin, petroleum resin, or the like can be used.
Examples of the anti-aging agent include 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,6-di- t-butyl-4-methylphenol, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis [3- (3,5-di-t-butyl) -4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexane-1,6-diylbis-3- (3,5 -Di-t-butyl-4-hydroxyphenylpropionamide), 3,5-bis (1,1-dimethylethyl) -4-hydroxyalkyl ester, die [{3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl} methyl] phosphonate, 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-t-butyl- a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-cresol, ethylenebis (oxyethylene) bis [3- (5-t-butyl-4-hydroxy-m-tolyl) ) Poropionate], tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetramethylthiuram monosulfide and the like.

In addition, a formaldehyde catcher agent, a filler, or the like may be added to the adhesive according to desired physical properties.
Examples of the formaldehyde catcher include pyrrolidine, piperidine, piperazine, morpholine, melamine, dicyandiamide, urea, ethylene urea, 4,5-dimethoxyethylene urea, propylene urea, 5-methylpropylene urea, 5-hydroxypropylene urea, 5- Methoxypropylene urea, oxalyl urea (parabanic acid), hydrazobenzothiazole, semicarbazide, thiosemicarbazide can be used, and formaldehyde which is a harmful volatile substance can be captured. As the filler, talc, calcium carbonate, clay, smectite, silica, hydrotalcite, mica and the like can be used.

Further, for the purpose of improving light resistance, an ultraviolet absorber such as benzotriazole or a light stabilizer such as hindered amine may be added to the adhesive.

Adhesive is suitably used for bonding / bonding paper, wood, cloth, leather, jersey, leather, rubber, plastic, foam, earthenware, glass, mortar, cement-based material, ceramic, metal, etc. be able to.

<Example 1>
[Production of acetoacetyl-modified chloroprene rubber]
Using a reactor having an internal volume of 5 liters, 12 parts of disproportionated rosin acid potassium salt Longis K-25 (Arakawa Chemical Industries, solid content 25%) in 100 parts of pure water under a nitrogen atmosphere, naphthalenesulfonic acid and A sodium salt of a formaldehyde condensate (trade name Demol N: manufactured by Kao) and 0.5 part of sodium hydroxide were dissolved. In this solution, 99.5 parts of chloroprene monomer, 0.5 part of 2-acetoacetoxyethyl methacrylate and 0.24 part of dodecyl mercaptan were added and emulsified, and then potassium persulfate was used as an initiator at 10 ° C. in a nitrogen atmosphere. Emulsion polymerization was performed. When the polymerization rate of chloroprene reached 75%, phenothiazine emulsion was added to terminate the polymerization. Subsequently, it heated under reduced pressure and collect | recovered the unreacted chloroprene monomer. The obtained polychloroprene latex was adjusted to pH 7 with dilute acetic acid and then made into a sheet by a conventional freeze coagulation method, which was dried to obtain an acetoacetyl-modified chloroprene rubber. The Mooney viscosity and acetoacetyl modification amount of the obtained acetoacetyl modified chloroprene rubber are shown in Table 1.

[Measurement of Mooney viscosity]
About the chloroprene rubber, the Mooney viscosity in 100 degreeC was measured based on JIS-K6300.

[Measurement of amount of acetoacetyl modification]
The obtained rubber sheet was purified with benzene and methanol and freeze-dried, dissolved in 5% deuterated chloroform solution, and measured using JNM-GSX-400 (400 MHz, FT type) manufactured by JEOL Ltd. . In this ¹ H-NMR spectrum, the peak area (A) of 4.0 to 6.2 ppm derived from the chloroprene structure and 4.2 derived from the acetoacetyl group based on the chloroform peak (7.24 ppm) in deuterated chloroform. It calculated from the following formula from the peak area (B) of ˜4.4 ppm.
Acetoacetyl modification amount (mol%) = (B / A) × 1/2

[Adhesive adjustment]
An alkylphenol resin (Tamanol 526: Arakawa Chemical Industries, Ltd.) 50 parts and magnesium oxide (Kyowa Mag # 150: Kyowa Chemical Industry Co., Ltd.) 3 parts are dissolved in 100 parts of a 1: 1 mixed solvent of cyclohexane and ethyl acetate at room temperature. And chelating reaction for 16 hours. Next, 100 parts of chloroprene rubber and a 1: 1 mixed solvent of cyclohexane and ethyl acetate are added to the cyclohexane solution so that the adhesive viscosity is 3,700-4,300 [mPa · s]. The mixture was mixed and stirred until completely dissolved, to obtain an adhesive. Table 1 shows the results of the viscosity, delamination resistance and peel strength of the adhesive.

[Measurement of viscosity of adhesive]
After creating the adhesive, the viscosity at 25 ° C. was measured using a Brookfield viscometer.

[Adhesive layer separation resistance test]
The adhesive was placed in a glass container and stored in a constant temperature water bath at 60 ° C. under light shielding. The appearance of the adhesive was observed over 8 weeks, and the week in which separation of the adhesive components was observed was recorded.

[Peel strength]
The peel strength test was performed according to the method defined in JIS K 6854-3: 1999, using canvas as the adherend. The obtained adhesive is applied to the canvas with a brush so that the application amount is about 300 g / m ² , and is left for 30 minutes after the final application, and then the adhesive-coated surfaces of the canvas are bonded together. And crimped. The laminated sample was cured at 23 ° C. for 7 days, then cut to a size of 200 × 25 mm, and a T-type peel test was performed at a rate of 200 mm / min in an atmosphere at 23 ° C.

<Example 2>
Polymerization was carried out under the same conditions as in Example 1, except that 98 parts of chloroprene monomer, 2 parts of 2-acetoacetoxyethyl methacrylate and 0.22 parts of dodecyl mercaptan, and an adhesive in the same manner as in Example 1. It was created. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance, and peel strength are shown in Table 1.

<Example 3>
Polymerization was carried out under the same conditions as in Example 1, except that 99 parts of chloroprene monomer, 1 part of 2-acetoacetoxyethyl methacrylate, 0.23 part of dodecyl mercaptan, and a polymerization rate of 85%. An adhesive was prepared in the same manner. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance, and peel strength are shown in Table 1.

<Example 4>
Polymerization was carried out under the same conditions as in Example 1, except that the chloroprene monomer was 95 parts, 2-acetoacetoxyethyl methacrylate was 5 parts, dodecyl mercaptan was 0.25 parts, the polymerization temperature was 35 ° C., and the polymerization rate was 65%. And an adhesive was prepared in the same manner as in Example 1. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance, and peel strength are shown in Table 1.

<Example 5>
Polymerization was carried out under the same conditions as in Example 1, except that chloroprene monomer was 93 parts, 2-acetoacetoxyethyl methacrylate was 7 parts, dodecyl mercaptan was 0.30 part, polymerization temperature was 15 ° C., and the polymerization rate was 65%. And an adhesive was prepared in the same manner as in Example 1. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance, and peel strength are shown in Table 1.

<Example 6>
Polymerization was carried out under the same conditions as in Example 1, except that the chloroprene monomer was 98 parts, 2-acetoacetoxyethyl methacrylate was 2 parts, dodecyl mercaptan was 0.27 parts, the polymerization temperature was 45 ° C., and the polymerization rate was 70%. And an adhesive was prepared in the same manner as in Example 1. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance, and peel strength are shown in Table 1.

<Example 7>
The same conditions as in Example 1 except that 96 parts of chloroprene monomer, 4 parts of 3-acetoacetoxypropyl methacrylate instead of 2-acetoacetoxyethyl methacrylate, 0.20 part of dodecyl mercaptan, and a polymerization rate of 70% Polymerization was carried out and an adhesive was prepared in the same manner as in Example 1. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance, and peel strength are shown in Table 1.

<Comparative Example 1>
Polymerization was carried out under the same conditions as in Example 1 except that the chloroprene monomer was 100 parts and dodecyl mercaptan was 0.12 parts, and an adhesive was prepared in the same manner as in Example 1. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance and peel strength are shown in Table 2.

<Comparative example 2>
Polymerization was carried out under the same conditions as in Example 1 except that the chloroprene monomer was 100 parts, the dodecyl mercaptan was 0.16 parts, the polymerization temperature was 35 ° C., and the polymerization rate was 65%. An adhesive was made. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance and peel strength are shown in Table 2.

<Comparative Example 3>
Polymerization was carried out under the same conditions as in Example 1 except that 93 parts of chloroprene monomer, 7 parts of 2-acetoacetoxyethyl methacrylate and 0.22 parts of dodecyl mercaptan were used. When prepared, the adhesive gelled. The results of Mooney viscosity ML (1 + 4) 100 ° C. and the amount of acetoacetyl modification are shown in Table 2.

<Comparative example 4>
Polymerization was performed under the same conditions as in Example 1 except that the polymerization rate was 65%, and an adhesive was prepared in the same manner as in Example 1. The results of Mooney viscosity ML (1 + 4) 100 ° C., acetoacetyl modification amount, adhesive viscosity, delamination resistance and peel strength are shown in Table 2.

Claims (6)

An acetoacetyl-modified chloroprene rubber containing acetoacetyl groups in an amount of 0.02 to 0.50 mol% in all polymers. The chloroprene monomer alone, or obtained by copolymerizing 0.5 to 10 parts by mass of an acetoacetylated monomer with respect to 100 parts by mass of a monomer that can be copolymerized with a chloroprene monomer and a chloroprene monomer. Acetoacetyl modified chloroprene rubber. The acetoacetylated monomer is at least one selected from allyl acetoacetate, vinyl acetoacetate, 2-acetoacetoxyethyl acrylate, 2-acetoacetoxyethyl methacrylate, 2-acetoacetoxypropyl acrylate, 2-acetoacetoxypropyl methacrylate 3. The acetoacetyl-modified chloroprene rubber according to claim 1 or 2. Mooney viscosity is 30-100ML (1 + 4) 100 degreeC, The acetoacetyl modified chloroprene rubber as described in any one of Claims 1-3 characterized by the above-mentioned. Chloroprene monomer alone or 100 parts by mass of a monomer copolymerizable with chloroprene monomer and chloroprene monomer and 0.5 to 10 parts by mass of acetoacetylated monomer 0.5 to 7 parts by mass of rosin acid and / or metal salt of rosin acid A method for producing an acetoacetyl-modified chloroprene rubber that undergoes an emulsion polymerization reaction in the presence of a part until the polymerization rate reaches 50% or more. An adhesive obtained by dissolving the acetoacetyl-modified chloroprene rubber according to any one of claims 1 to 4 in an organic solvent.