JP2021001297A - Method for producing chloroprene polymer latex and method for producing adhesive - Google Patents

Abstract

To provide a method for producing a chloroprene polymer latex used for a chloroprene adhesive, offering a highly good balance between initial adhesion and heat resistance.SOLUTION: A method for producing a chloroprene polymer latex includes, in the presence of an emulsifier and a chain transfer agent, subjecting chloroprene to emulsion radical homopolymerization, or subjecting chloroprene and a monomer copolymerizable with the chloroprene to emulsion radical copolymerization. When the monomer content is 100 pts.mass, the content of the emulsifier is 6.0 pts.mass or more and 8.0 pts.mass or less and the content of the chain transfer agent is 0.085 pts.mass or more and 0.100 pts.mass or less, and the polymerization temperature is 0°C or higher and 20°C or lower.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a chloroprene polymer latex and a method for producing an adhesive containing the latex.

Conventionally, vinyl acetate-based polymers, chloroprene-based polymers, acrylic acid ester-based polymers, natural rubber, urethane-based polymers and the like are known as polymers for adhesives. Among them, chloroprene-based polymers are suitably used for adhesive applications such as organic solvent-based contact adhesives because they can obtain a high degree of adhesive strength with low pressure bonding to a wide range of adherends. However, from the viewpoint of environmental pollution and consideration for human health in recent years, VOC regulations and solvent regulations have been called for many years, and in response to these demands, the development of water-based adhesives that do not use organic solvents is underway, and chloroprene weight Water-based adhesives containing coalesced latex have been proposed.

However, the water-based adhesive has a problem that the adhesive strength is lower than that of the conventional organic solvent-based adhesive. Therefore, in order to increase the adhesive strength, particularly the initial adhesive strength, it has been proposed to reduce the molecular weight of the chloroprene polymer to improve the motility of the molecule and improve the film-forming property and the wettability to the adherend. It is stated that this method improves the initial adhesive strength. However, if the initial adhesive strength is improved, the cohesive force between the chloroprene polymer molecules is reduced, so that the heat resistance is lowered and the final product cannot be used as an adhesive for furniture and mattresses, which requires heat resistance during transportation. ..

On the other hand, in order to increase the heat resistance, it has been proposed to increase the molecular weight of the chloroprene polymer to increase the cohesive force. It is described that this method improves heat resistance. However, if the heat resistance is improved, the film-forming property and the wettability to the adherend are lowered, so that the initial adhesive force is lowered and the foam adhesive cannot be used for furniture, mattresses and the like, which require quick bonding.
As described above, there is a trade-off relationship between the initial adhesive strength and the heat resistance of the chloroprene-based adhesive, and if any of them is improved, one of them will decrease.

Japanese Patent No. 5221353 Japanese Patent No. 4180195 Japanese Patent No. 5405258

An object of the present invention is to provide the above-mentioned problem in a chloroprene-based adhesive, that is, a method for producing an adhesive having a high dimension and an excellent balance between initial adhesive force and heat resistance.

The present inventors have found that the above-mentioned problems can be solved by emulsion polymerization of chloroprene under specific conditions, and have completed the present invention.
One aspect of the present invention is as follows.
[1] A method for producing a chloroprene polymer latex by homopolymerizing chloroprene with an emulsifying radical in the presence of an emulsifier and a chain transfer agent, or by copolymerizing chloroprene and a monomer copolymerizable with the chloroprene with an emulsifying radical. ,
The amount of the emulsifier is 6.0 parts by mass or more and 8.0 parts by mass or less when the monomer is 100 parts by mass, and the amount of the chain transfer agent is 0.085 parts by mass when the monomer is 100 parts by mass. A production method comprising 0.100 parts by mass or less and a polymerization temperature of 0 ° C. or higher and 20 ° C. or lower.
[2] The method for producing a chloroprene polymer latex according to 1 above, wherein the emulsifier is potassium rosinate, sodium rosinate or a mixture thereof.
[3] The method for producing a chloroprene polymer latex according to 1 or 2 above, wherein the chain transfer agent is an alkyl mercaptan.
[4] From the step of producing a chloroprene polymer latex by the method according to any one of the above 1 to 3 and an additive selected from a tackifier, an acid receiving agent and an antioxidant to the obtained latex. A method for producing an adhesive, which comprises an optional step of mixing at least one of the additives selected.
[5] A step of producing a chloroprene polymer latex by the method according to any one of 1 to 3 above, a step of mixing the chloroprene polymer latex with an acrylic polymer latex having a glass transition point of 0 ° C. or less, and A method for producing an adhesive, which comprises an optional step of mixing at least one of an additive selected from an additive selected from a tackifier, an acid receiver and an antioxidant with a chloroprene polymer latex.

According to one embodiment of the present invention, in emulsified radical polymerization of chloroprene, the amount of emulsifier is controlled to reduce the particle size of the polymer, and the amount of chain transfer agent is controlled to optimize the molecular weight. The obtained adhesive containing the chloroprene polymer latex can improve the initial adhesive strength without lowering the heat resistance, and thus can balance the initial adhesive strength and the heat resistance at a high level.

An embodiment of the present invention will be described in detail below. It should be noted that the present embodiment shows an example of the present invention, and the present invention is not limited to the present embodiment. In addition, various changes or improvements can be made to the present embodiment, and the modified or improved forms may be included in the present invention.

In the present specification, the chloroprene polymer latex refers to a lipophilic chloroprene polymer emulsified by an emulsifier and dispersed in water as particles.
In the present specification, the chloroprene polymer includes not only a chloroprene homopolymer but also a copolymer of chloroprene and another monomer.

In one embodiment of the production method of the present invention, chloroprene is homopolymerized with an emulsion radical in the presence of an emulsifier and a chain transfer agent, or chloroprene and a monomer copolymerizable with the chloroprene are copolymerized with an emulsion radical to produce a chloroprene polymer. It is a method for producing a chloroprene polymer latex by allowing the chloroprene polymer to be produced (the emulsion radical homopolymerization and the emulsion radical copolymerization may be combined and simply referred to as emulsion radical polymerization or emulsion polymerization).

Chloroprene is 2-chloro-1,3-butadiene.
The monomer copolymerizable with chloroprene is not particularly limited as long as it can be copolymerized with chloroprene, but for example, 2,3-dichloro-1,3-butadiene, 1-chloro-1, Examples thereof include 3-butadiene, butadiene, isoprene, styrene, methacrylic acid, acrylic acid, itaconic acid, 2-methyl-2-pentenoic acid and 2-butylpropenic acid. As the monomer copolymerizable with chloroprene, one type may be used alone, or two or more types may be used in combination. The amount of this monomer used may be within a range that does not significantly impair the effects of the present invention, but specifically, it is preferably 3% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less of all the monomers. preferable.

The emulsion polymerization adopted in one embodiment of the present invention is industrially aqueous emulsion polymerization.

As the emulsifier used for emulsion radical polymerization, an anionic emulsifier is preferable. In particular, potassium rosinate, sodium rosinate, or a mixture thereof is preferable because it is easy to stabilize the colloidal state and destabilize for forming an adhesive layer by adjusting the pH.

The amount of the emulsifier used is 6.0 to 8.0 mass with respect to 100 parts by mass of the monomer (the amount of chloroprene in the case of homopolymerization, the total amount of monomers copolymerizable with chloroprene in the case of copolymerization). It is a department. 6.2 to 7.5 parts by mass is more preferable, and 6.5 to 7.0 parts by mass is further preferable. By setting the amount of the emulsifier to 6.0 parts by mass or more, the particle size of the chloroprene polymer can be sufficiently reduced and the film forming property at the time of pressurization when used as an adhesive is improved, which is preferable. On the other hand, by setting the amount of the emulsifier to 8.5 parts by mass or less, the dehydrochloration rate over time can be slowed down, the storage stability of latex can be improved, and the emulsion stability when blended as an adhesive can be improved. Is preferable because agglomeration is less likely to occur.

In the emulsification radical polymerization, an emulsification aid can be used in addition to the above emulsifier. Examples of the emulsifying aid include dodecylbenzene sulfonates such as sodium dodecylbenzene sulfonic acid, potassium dodecylbenzene sulfonic acid, and triethanolamine dodecylbenzene sulfonic acid, sodium diphenyl ether sulfonic acid salt, and ammonium diphenyl ether sulfonic acid salt. Diphenyl ether sulfonate system, naphthalene sulfonate system such as sodium salt of β-naphthalene sulfonic acid formaldehyde condensate and the like. Moreover, as a nonionic emulsification aid, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene lauryl ether and the like can be mentioned.

When these emulsifying aids are blended, the amount thereof is 0. When the amount of the monomer (the amount of chloroprene in the case of homopolymerization and the total amount of the monomers copolymerizable with chloroprene in the case of copolymerization) is 100 parts by mass. 05 to 1.0 parts by mass is preferable, and 0.1 to 0.5 parts by mass is more preferable. By using the emulsification aid in combination, aggregation between latex particles is suppressed, and emulsion stability and storage stability over time are improved.

Chain transfer agents are mainly used to regulate molecular weight and molecular weight distribution. Examples of the chain transfer agent used in one embodiment of the present invention include dialkylxanthogen disulfide, alkyl mercaptan and the like.
Examples of the dialkylxanthogen disulfide include diisopropylxanthogen disulfide, diethylxantogen disulfide, dicyclohexylxanthogen disulfide, dilaurylxantogen disulfide, dibenzylxantogen disulfide and the like. Examples of the alkyl mercaptan include n-dodecyl mercaptan, n-decyl mercaptan and octyl. Examples include mercaptan. It is also possible to use two or more types of chain transfer agents in combination as long as the object of the present invention is not impaired.
Among them, alkyl mercaptans whose molecular weight can be easily adjusted are preferable, alkyl mercaptans having 7 to 15 carbon atoms are more preferable, and n-dodecyl mercaptans are even more preferable.
The amount of the chain transfer agent used is 0.085 to 0 when the amount of the monomer (the amount of chloroprene in the case of homopolymerization and the total amount of the monomer copolymerizable with chloroprene in the case of copolymerization) is 100 parts by mass. It is 100 parts by mass. It is preferably 0.087 to 0.098 parts by mass, more preferably 0.089 to 0.095 parts by mass.

A radical polymerization initiator can be used for the emulsified radical polymerization. As the radical polymerization initiator, a normal radical polymerization initiator can be used without limitation. Specific examples of the polymerization initiator include organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate and ammonium persulfate, and azo compounds such as azobisisobutyronitrile. In addition, a co-catalyst such as anthraquinone sulfonate, potassium sulfite, and sodium sulfite can be used together with the polymerization initiator. As the polymerization initiator or co-catalyst, one type may be used alone, or two or more types may be used in combination.

The pH of the polymerization solution is preferably in the range of 5.5 or more and 13.5 or less, more preferably 6.0 or more and 13.5 or less, and further preferably 10.0 or more and 13.0 or less. is there. It is preferable to set the pH to 5.5 or higher because the emulsified state is stable and the chloroprene polymer particles do not aggregate. When the pH is 13.5 or less, the ionic strength becomes small and it is preferable that the colloidal particles do not aggregate.

The pH can be adjusted using a base, an acid, an amino acid or the like. Examples of the base include an aqueous solution of amines such as diethanolamine and triethanolamine, and metal hydroxides such as potassium hydroxide and sodium hydroxide. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and boric acid, and organic acids such as acetic acid and citric acid. Examples of amino acids include glycine and alanine.

In one embodiment of the invention, the polymerization temperature is 0-20 ° C. 3 to 18 ° C is preferable, and 5 to 15 ° C is more preferable. It is preferable to set the polymerization temperature to 0 ° C. or higher because the productivity of the polymer is sufficient, and it is preferable to set the polymerization temperature to 20 ° C. or lower because the initial adhesive strength is sufficient.

In one embodiment of the production method of the present invention, the polymerization conversion rate is preferably 65% to 80%, more preferably 70 to 79%, still more preferably 75 to 78%. When the polymerization conversion rate is 65% or more, the solid content of the polymer latex increases, and when used as an adhesive, the energy load in the drying process after application to the adherend is small, and the adhesive layer can be easily made uniform. preferable. Further, when the polymerization conversion rate is 65% or more, the amount of monomers remaining in the latex is reduced, odors due to the monomers are less likely to occur, and cohesive force and adhesive force are not deteriorated, which is preferable. On the other hand, when the polymerization conversion rate is 80% or less, there are few branches in the polymer and the molecular weight distribution is narrow, so that the adhesive strength is good.

Here, the polymerization conversion rate can be obtained as follows.
The chloroprene polymer latex is dried by heat treatment (at 141 ° C. for 30 minutes) to obtain only the solid content, and the solid content concentration (S) is calculated from the mass before drying and the mass after drying. The solid content concentration (theoretical value) when the polymerization reaction proceeds 100% is theoretically calculated, and this theoretical value is defined as T ₁₀₀ . The solid content concentration (theoretical value) at 0% progress of the polymerization reaction is theoretically calculated, and this theoretical value T ₀ is used. Then, the polymerization conversion rate (unit:%) is calculated by the following formula.
Polymerization conversion rate = (ST ₀ ) / (T ₁₀₀ −T ₀ ) × 100

The polymerization conversion rate can be controlled by adding a polymerization terminator to stop the polymerization reaction when the target conversion rate is reached. The polymerization inhibitor that can be used in the present invention is not particularly limited as long as it is generally used for emulsion radical polymerization, and examples thereof include phenothiazine, para-t-butylcatechol, hydroquinone, hydroquinone monomethyl ether, and diethylhydroxylamine.

In one embodiment of the production method of the present invention, the chloroprene polymer latex is polymerized so that the gel content in the solid content, that is, the gel content is 5% by mass or less of the chloroprene polymer contained in the latex. Is preferable. A more preferable gel content is 4% by mass or less, and a more preferable gel content is 3% by mass or less. If the gel content exceeds 5% by mass, the wettability when applied as an adhesive when chloroprene polymer latex is used as an adhesive may decrease, and if the wettability decreases, the adhesive strength decreases. There is. The gel means a polymer component insoluble in tetrahydrofuran.

In one embodiment of the production method of the present invention, the tetrahydrofuran-soluble content in the solid content of the chloroprene polymer latex has a weight average molecular weight (Mw) of 770,000 to 1.05 million as measured by its GPC (gel permeation chromatography). It is preferable to polymerize so as to become. A more preferable Mw is 800,000 to 1,000,000, and a more preferable Mw is 85 to 950,000. By setting Mw to 770,000 or more, good heat resistance can be obtained when the obtained chloroprene polymer latex is used as an adhesive, which is preferable. On the other hand, when Mw is 1.05 million or less, good initial adhesive strength can be obtained when the obtained chloroprene polymer latex is used as an adhesive, which is preferable.
The above average molecular weight can be adjusted by the amount of the chain transfer agent added, and the larger the amount of the chain transfer agent added, the lower the molecular weight of the chloroprene polymer can be obtained.

In one embodiment of the production method of the present invention, it is preferable to carry out polymerization so that the molecular weight distribution (Mw / Mn) of the above-mentioned tetrahydrofuran-soluble component is 1.9 to 3.2. The more preferable Mw / Mn is 2.1 to 3.0, and the more preferable Mw / Mn is 2.3 to 2.8. By setting Mw / Mn to 1.9 or more, when the obtained chloroprene polymer latex is used as an adhesive, initial adhesion and heat resistance are good, which is preferable. On the other hand, when Mw / Mn is set to 3.2 or less, the adhesive strength becomes good when the obtained chloroprene polymer latex is used as an adhesive, which is preferable.

In one embodiment of the production method of the present invention, it is preferable to polymerize the obtained chloroprene polymer so that the volume average particle size is 62 to 88 nm. A more preferable volume average particle size is 66 to 84 nm, and a more preferable volume average particle size is 70 to 80 nm. By setting the volume average particle diameter to 62 nm or more, the obtained chloroprene polymer does not aggregate, and better heat resistance can be obtained when the latex is used as an adhesive, which is preferable. On the other hand, it is preferable that the volume average particle diameter is 88 nm or less because a better initial adhesive force can be obtained when the obtained chloroprene polymer latex is used as an adhesive.

This is considered to be due to the following reasons.
When the adherend is crimped in a wet state after the adhesive is applied, the chloroprene polymer particles in the latex are in a state close to close packing. At this time, the gap between the particles becomes narrower as the particles become smaller. It is presumed that the capillary phenomenon works more strongly in the narrow gap and the water drainage progresses rapidly, so that the film formation and the subsequent crystallization proceed quickly, and as a result, the initial adhesive force is improved.
The average particle size can be adjusted by the polymerization conditions, and particularly by the amount of emulsifier.

The volume average particle size can be measured by using a solution obtained by diluting latex 1000 to 10000 times with pure water, for example, using a dynamic light scattering photometer (ZETASISER (registered trademark) Nano-S manufactured by Malvern Panasonical Ltd). it can.

In one embodiment of the production method of the present invention, a step of removing unreacted monomers and volatile components can be provided after the chloroprene polymerization step. Further, the cooling step, the polymerization reaction aging step, or the heating step may be provided before or after the chloroprene polymerization step, or both.

Stabilizers such as antacids and antioxidants can be added to the chloroprene polymer latex produced by one embodiment of the production method of the present invention.
When an acid receiving agent is added, the amount added is preferably 0.01 part by mass or more and 10.0 part by mass or less, and 0.1 part by mass or more and 8.0 part by mass or less with respect to 100 parts by mass of the chloroprene polymer. More preferably, it is 0.5 parts by mass or more and 5 parts by mass or less.
When an antioxidant is added, the amount added is preferably 0.1 part by mass or more and 3.0 parts by mass or less, and 0.5 parts by mass or more and 2.5 parts by mass or less with respect to 100 parts by mass of the chloroprene polymer. More preferably, it is 0.5 parts by mass or more and 2.0 parts by mass or less.

By adding the stabilizer within the above range, the stability over time of the flexibility of the adhesive layer formed by drying the chloroprene polymer latex can be improved. When the amount of the antacid added is within the above range, the desorbed hydrochloric acid generated from the chloroprene polymer over time is sufficiently neutralized, and the deterioration of the latex due to the acid is suppressed. In addition, the colloidal stability of the chloroprene polymer latex is improved, and problems such as precipitation are less likely to occur. When the amount of the antioxidant added is within the above range, a sufficient antioxidant effect can be obtained and deterioration of the latex is suppressed.

When the stabilizer is insoluble in water or is a compound that destabilizes the colloidal state of the chloroprene polymer latex, a dispersion in which the stabilizer is dispersed in water is prepared in advance, and the dispersion is chloroprene weight. It may be added to the coalesced latex.

The type of antacid is not particularly limited, and examples thereof include zinc oxide and hydrotalcite (for example, trade names DHT-4A (registered trademark) and DHT-6 manufactured by Kyowa Chemical Industry Co., Ltd.). .. One type of antacid may be used alone, or two or more types may be used in combination.

The type of antioxidant is not particularly limited, but from the viewpoint of stain resistance, di (4-octylphenyl) amine, p- (p-toluenesulfonylamide) diphenylamine, 4,4'-bis ( Diphenylamine-based antioxidants such as α, α-dimethylbenzyl) diphenylamine are preferred. From the viewpoint of ozone resistance, N, N'-diphenyl-p-phenylenediamine (DPPD) or N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD) may be used. However, a hindered phenolic antioxidant is preferably used when discoloration or hygiene of the protruding portion of the adhesive when used as an adhesive is regarded as a problem.

In addition to the above stabilizers (antacids, antioxidants), chloroprene polymer latex may optionally contain fillers, tackifiers, pigments, colorants, wetting agents, defoamers, thickeners, etc. Can be added.

The adhesive according to one embodiment of the present invention comprises the chloroprene polymer latex produced by the above method, and is preferably a one-component water-based adhesive. The term adhesive also includes adhesives.
As the adhesive according to one embodiment of the present invention, an acrylic polymer latex (emulsion) can be mixed with the chloroprene polymer latex for the purpose of improving the initial adhesive strength of the adhesive. The acrylic polymer latex has a glass transition point (Tg) of preferably 0 ° C. or lower, more preferably −10 ° C. or lower, and even more preferably −20 ° C. or lower. When the glass transition point is 0 ° C. or lower, a flexible adhesive layer can be formed.

The acrylic polymer latex is preferably incompatible with chloroprene, and is a polymer latex using an acrylic compound as a monomer. Examples of the acrylic compound include (meth) acrylic acid, fumaric acid, maleic acid, and the like. Examples thereof include (meth) acrylamide and derivatives thereof; N-substituted maleimide compounds; itaconic acid, crotonic acid, phthalic acid and their esters, their metal salts, ammonium salts and the like. Preferred acrylic compounds include n-butyl methacrylate, 2-ethylhexyl methacrylate and itaconic acid.

The mixing ratio of the acrylic polymer latex is preferably 0.10 to 0.70, more preferably 0.17 to 0.50, based on the solid content mass, when the chloroprene polymer latex is 1. 25 to 0.45 is more preferable. When the mixing ratio is in this range, the initial adhesive strength is improved, which is preferable.

The adhesive according to one embodiment of the present invention may contain a tackifier for the purpose of improving the adhesive strength.
The type of the tackifier is not particularly limited, and examples thereof include phenolic resins, terpene resins, rosin derivative resins, and petroleum hydrocarbons. Specific examples include hydrogenated rosin, pentaerythritol ester of hydrogenated rosin, polymerized rosin, rosin-modified resin containing rosin as a main component, alkylphenol resin, rosin-modified phenol resin, terpene-modified phenol resin, and natural terpene resin. One type of tackifier may be used alone, or two or more types may be used in combination.

When the tackifier is contained, the content thereof is preferably 60 parts by mass or less, more preferably 20 parts by mass or more and 55 parts by mass or less, and 25 parts by mass or more and 50 parts by mass with respect to 100 parts by mass of the solid content of the chloroprene polymer latex. Less than a part is more preferable. When a tackifier is contained in a system in which an acrylic polymer latex is mixed with a chloroprene polymer latex, the content thereof is preferably 60 parts by mass or less based on 100 parts by mass of the sum of the solid contents of both latexes. More than 45 parts by mass, more preferably 20 parts by mass or more and 40 parts by mass or less. When the amount of the tackifier is within the above range, the adhesiveness is sufficiently ensured and the adhesive strength can be sufficiently improved.

The method of blending the tackifier is not particularly limited, but it can be carried out, for example, by adding the tackifier to the chloroprene polymer latex in the form of an emulsified and dispersed emulsion.

The adhesive in one embodiment of the present invention may further contain an acid receiver, an antioxidant, a filler, a pigment, a colorant, a wetting agent, an antifoaming agent, a thickener and the like. These can be the same as those described above.

The adherend is not particularly limited, and examples thereof include foams made of materials such as polyurethane, ethylene-vinyl acetate copolymer, and polyethylene, wood, cloth, and woven fabrics. More specifically, it can be suitably used for adhesion of a porous or water-absorbent base such as polyurethane foam to each other, polyurethane foam to wood, or wood to each other, for example, for bonding polyurethane foam mattresses and furniture.

The adhesive according to one embodiment of the present invention has an excellent balance between initial adhesive strength and heat resistance, for example, an initial adhesive strength of 25 N or more and a heat resistance of 70 ° C. or higher (initial adhesive strength and heat resistance). The evaluation method of is as described in Examples described later).

The present invention will be specifically described below with reference to Examples and Comparative Examples. The methods for evaluating the physical properties used in the examples and comparative examples are as follows.

(1) Gel content:
The latex is dried by heat treatment (at 141 ° C. for 30 minutes) to obtain only the solid content, and the solid content concentration is calculated from the mass before drying and the mass after drying.
On the other hand, 1 g of latex is added dropwise to 100 mL of tetrahydrofuran (sometimes referred to as THF) (manufactured by Junsei Chemical Co., Ltd., special grade), shaken for 24 hours, and then centrifuged (Cooling high-speed centrifuge H manufactured by Kokusan Co., Ltd.). Centrifuge at 14000 rpm for 60 minutes at -9R) to separate the dissolved phase of the supernatant, evaporate and dry the dissolved phase over 1 hour at 100 ° C., and measure the mass of the dried product.
The solid content mass in 1 g of latex is calculated from the above solid content concentration, the insoluble content mass is calculated by subtracting the dissolved content mass from the solid content mass, and the insoluble content mass with respect to the dissolved content mass is defined as the gel content (%). To do.
Solid content (mass%) = [(141 ° C., mass after drying for 30 minutes) / (mass of latex before drying)] × 100
Gel content (%) = {1-[(mass of dry matter (g)) / (solid content in 1 g of chloroprene polymer latex (g))]} × 100

(2) Average molecular weight (Mw, Mn) and molecular weight distribution (Mw / Mn) of the chloroprene polymer:
For the dissolved phase obtained by measuring the gel content, the polystyrene-equivalent molecular weight was measured by the gel permeation (GPC) method, and the weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured. (Mw / Mn) was calculated.
The GPC measurement conditions are as follows.
Equipment: Yokogawa Analytical Systems, HP1050 series,
Detector: Showa Denko Corporation Shodex® RI-71 (differential refractive index detector),
Column type: PLgel 10 μm MiniMIX-B manufactured by Agilent Technologies, Inc.
Column temperature: 40 ° C,
Eluent: Tetrahydrofuran (manufactured by Kanto Chemical Co., Inc., for HPLC),
Outflow rate: 0.4 mL / min

(3) Volume average particle size of chloroprene polymer:
The volume average particle size of the solution obtained by diluting the latex 1000 to 10000 times with pure water was measured using a dynamic light scattering photometer (ZETASISER® Nano-S manufactured by Malvern Panalytic Ltd).

(4) Initial adhesive strength of adhesive:
Density 32 kg / m ³ , 10 cm x 20 cm x 2 cm polyurethane foam (Bridgestone Kasei Co., Ltd., Everlight (registered trademark) TMW) with the 10 cm x 20 cm side facing the top surface, half of the top surface (10 cm x 10 cm) 1 g of the adhesive was applied to the surface with a spray gun (W-101-131G manufactured by Anest Iwata Co., Ltd.). Another 10 cm x 20 cm x 2 cm polyurethane foam in a 10 cm x 10 cm area was overlapped with the adhesive-coated portion and pressure-bonded with a force of 6 kg for 5 seconds. After 1 minute, a tensile test was performed at a speed of 200 mm / min in the direction of the adhesive-coated surface with a tensile measuring machine to measure the shear peel strength. The test environment is a temperature of 23 ± 3 ° C. and a humidity of 50 ± 10%.

(5) Heat resistance of adhesive:
Apply adhesive to a spray gun (W-101-131G manufactured by Anest Iwata Co., Ltd.) in half (5 cm x 8 cm) on each 8 cm x 10 cm surface of two pieces of polyurethane foam with a density of 32 kg / m ³ and 8 cm x 10 cm x 3 cm. Apply 0.4 g each. After application, the adhesive surfaces are overlapped so that the entire foam overlaps, and the adhesive surfaces are compressed with a force of 5 kg for 5 seconds. Dry at 23 ° C. and 50% RH (relative humidity) for 2 days. One test piece is hung in an oven (DKN402 manufactured by Yamato Scientific Co., Ltd.) so as to be in the T-type peeling mode, and a weight of 200 g is hung on the lower end of the other test piece. Keep the oven temperature at 40 ° C. for 30 minutes. Immediately after that, the temperature is raised to 5 ° C., and after the temperature is raised, the temperature is maintained for 30 minutes. This heating process is repeated and the evaluation is carried out until the temperature is maintained at 100 ° C. for 30 minutes. The temperature at which the adhesive surface is peeled off by 1 cm over the entire width (8 cm) is defined as the heat resistant temperature.

(6) Glass transition point (Tg):
Weigh 2 ml of acrylic polymer latex on an aluminum dish (diameter 4 cm), heat it to 105 ° C in an oven (DKN402 manufactured by Yamato Scientific Co., Ltd.), dry it for 30 minutes while maintaining 105 ° C, and measure the sample. And said.
Using DSC7200 manufactured by Seiko Instruments Inc., the intermediate point glass transition temperature Tmg was determined as Tg according to the method of heat flux differential scanning calorimetry specified in JIS K7121-2012.

Example 1
Chloroprene (manufactured by Tokyo Kasei Kogyo Co., Ltd.) 20 kg, n-dodecyl mercaptan (manufactured by Tokyo Kasei Kogyo Co., Ltd.) 18 g, potassium logite (manufactured by Arakawa Chemical Co., Ltd., R-300) 1300 g in a reactor with an internal volume of 60 liters. , 17 kg of ion-exchanged water, 340 g of potassium hydroxide (manufactured by Junsei Chemical Co., Ltd., special grade), and 20 g of potassium sulfite were charged and emulsified. Then, using potassium persulfate as an initiator, polymerization was carried out at 10 ° C. under a nitrogen gas atmosphere. After 400 minutes, the predetermined polymerization conversion rate (77%) was reached, and an emulsion of phenothiazine was immediately added to terminate the polymerization to obtain a chloroprene polymer latex. The solid content concentration of this latex was 45% by mass.
This latex was steam distilled under reduced pressure to remove residual chloroprene monomer. The gel content, weight average molecular weight and molecular weight distribution of the chloroprene polymer latex from which the chloroprene monomer had been removed were measured, and the results are shown in Table 1.

70 g of chloroprene polymer latex (solid content concentration: 45%) from which chloroprene monomer has been removed and 30 g of acrylate-based latex (Nipol (registered trademark) LX874 manufactured by Nippon Zeon Co., Ltd., solid content concentration: 45%, Tg: -31 ° C.) It was placed in a 150 ml plastic cylindrical container and stirred with a three-one motor (registered trademark) for 5 minutes. Next, 1.5 g of glycine (manufactured by Showa Denko KK) was added while stirring with a three-one motor (registered trademark), the pH was adjusted to 9.0 at 23 ° C., and another 5 with a three-one motor (registered trademark). Stir for minutes to obtain an adhesive. The initial adhesive strength (adhesive strength) and heat resistance (heat resistant temperature) of the obtained adhesive were evaluated, and the results are shown in Table 1.

Comparative Examples 1 to 6:
In Example 1, the same procedure as in Example 1 was carried out except that the amounts of potassium rosinate (emulsifier) and n-dodecyl mercaptan (chain transfer agent) were changed to the amounts shown in Table 1, and the chloroprene polymer latex and The adhesive was manufactured and the evaluation results are shown in Table 1.

From Table 1, the adhesive using the latex produced in Example 1 has a high-dimensional and excellent balance of initial adhesive strength and heat resistance.

Claims (5)

A method for producing a chloroprene polymer latex by homopolymerizing chloroprene with an emulsifying radical in the presence of an emulsifier and a chain transfer agent, or by copolymerizing chloroprene and a monomer copolymerizable with the chloroprene with an emulsifying radical.
The amount of the emulsifier is 6.0 parts by mass or more and 8.0 parts by mass or less when the monomer is 100 parts by mass, and the amount of the chain transfer agent is 0.085 parts by mass when the monomer is 100 parts by mass. A production method comprising 0.100 parts by mass or less and a polymerization temperature of 0 ° C. or higher and 20 ° C. or lower. The method for producing a chloroprene polymer latex according to claim 1, wherein the emulsifier is potassium rosinate, sodium rosinate, or a mixture thereof. The method for producing a chloroprene polymer latex according to claim 1 or 2, wherein the chain transfer agent is an alkyl mercaptan. A step of producing a chloroprene polymer latex by the method according to any one of claims 1 to 3, and an additive selected from a tackifier, an acid accepting agent and an antioxidant for the obtained latex. A method for producing an adhesive, which comprises an optional step of mixing at least one of the additives. A step of producing a chloroprene polymer latex by the method according to any one of claims 1 to 3, a step of mixing an acrylic polymer latex having a glass transition point of 0 ° C. or less with the chloroprene polymer latex, and a chloroprene weight. A method for producing an adhesive, which comprises an optional step of mixing at least one of an additive selected from an additive selected from a tackifier, an acid receiving agent and an antioxidant with the combined latex.