JP4133152B2 - Method for producing copolymer latex for rubber foam - Google Patents

Description

【００５８】
【表２】

【００５９】
【発明の効果】
以上のとおり、本発明は弾力性と風合いのバランスに優れたきめ細かなゴム発泡体の製造に使用される共重合体ラテックス、更には、ゴム発泡体を製造する際の発泡工程からゲル化工程まで、きめ細かな発泡構造と発泡倍率を保ち、弾力性と風合いのバランスに優れたきめ細かなゴム発泡体を安定に効率よく生産することを可能にするゴム発泡体用共重合体ラテックスを提供することができる。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a copolymer latex used for the production of a fine rubber foam having an excellent balance between elasticity and texture.Manufacturing methodAbout. In more detail, from the foaming process to the gelling process when manufacturing rubber foam, it maintains a fine foam structure and expansion ratio, and stably and efficiently produces fine rubber foam with excellent balance between elasticity and texture. Copolymer latex for rubber foam that makes it possible toManufacturing methodAbout.
[0002]
[Prior art]
Rubber foams made from copolymer latex as a raw material through foaming, gelation, vulcanization, washing, and drying processes are made of various impact absorbing materials, sound insulating materials, sound absorbing materials, oil-drawn materials, Used as a sponge core for mattresses and cushions, and as a puff for makeup. Among these applications, oil-resistant materials, cosmetic puffs, and the like are required to have oil resistance, and so far, copolymer latex of acrylonitrile and butadiene has been preferably used. In particular, various proposals such as Patent Documents 1 to 5 have been proposed so far for the purpose of improving the characteristics of cosmetic puffs. It was still insufficient to stably and efficiently produce a fine rubber foam having a stable foam structure and expansion ratio and excellent balance between elasticity and texture.
[0003]
[Patent Document 1]
JP-A-6-14811
[Patent Document 2]
JP-A-6-32942
[Patent Document 3]
JP-A-6-73220
[Patent Document 4]
JP-A-6-73221
[Patent Document 5]
Japanese Patent Laid-Open No. 11-263846
[0004]
[Problems to be solved by the invention]
  The present invention relates to a copolymer latex used for the production of a fine rubber foam having an excellent balance between elasticity and texture.Manufacturing methodIn addition, from the foaming process to the gelling process when manufacturing rubber foams, it maintains a fine foam structure and expansion ratio, and stably and efficiently produces fine rubber foams with excellent balance of elasticity and texture. Copolymer latex for rubber foam that makes it possible toManufacturing methodThe purpose is to provide.
[0005]
[Means to solve the problem]
  As a result of intensive investigations to solve the current problems in view of the above-mentioned circumstances, the present inventors have devised the copolymer latex so that the rosin soap and the fatty acid soap are in a specific range, so that the above problem Has been found to be solved, and the present invention has been completed.
  That is, the present invention
  Emulsifying monomer comprising 50 to 90 parts by weight of aliphatic conjugated diene monomer, 10 to 40 parts by weight of vinyl cyanide monomer, and 0 to 20 parts by weight of other monomers copolymerizable therewith An emulsion polymerization step for obtaining a copolymer latex by polymerization, a concentration step for concentrating the copolymer latex to a solid content concentration of 60% by weight or more, and 100 weight for the copolymer latex (in terms of solid content) An addition step of adding 0.3 to 3.5 parts by weight of rosin acid soap and 0.3 to 3.5 parts by weight of fatty acid soap in terms of solid content, in the emulsion polymerization step, the rosin A method for producing a copolymer latex for rubber foam, characterized by adding acid soap and / or fatty acid soapIs to provide.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
Examples of the aliphatic conjugated diene monomer in the present invention include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene. Examples include butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like, and one or more of them can be used. In particular, the use of 1,3-butadiene is preferred.
[0007]
Examples of the vinyl cyanide monomer in the present invention include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and the like, and one or more of them can be used. In particular, the use of acrylonitrile or methacrylonitrile is preferred.
[0008]
Other monomers copolymerizable with the above monomers include aromatic vinyl monomers, ethylenically unsaturated carboxylic acid alkyl ester monomers, ethylenically unsaturated monomers containing hydroxyalkyl groups, Examples thereof include an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated carboxylic acid amide monomer.
[0009]
Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, methyl α-methylstyrene, vinyltoluene and divinylbenzene, and these can be used alone or in combination of two or more.
[0010]
Examples of ethylenically unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaco Nate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like can be used, and one or more of these can be used. In particular, use of methyl methacrylate or butyl acrylate is preferable.
[0011]
Examples of the ethylenically unsaturated monomer containing a hydroxyalkyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2- Hydroxypropyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2-hydroxyethyl methyl fumarate, and the like. 1 type (s) or 2 or more types can be used.
[0012]
Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. It can be used above.
[0013]
Examples of the ethylenically unsaturated carboxylic acid amide monomer include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N-dimethylacrylamide, and the like, and one or more of these are used. be able to.
[0014]
The above-mentioned monomer composition constituting the copolymer latex of the present invention is composed of 50 to 90 parts by weight of an aliphatic conjugated diene monomer, 10 to 40 parts by weight of a vinyl cyanide monomer, and a copolymer with them. It should be 0-20 parts by weight of other possible monomers.
[0015]
If the aliphatic conjugated diene monomer is less than 50 parts by weight, the texture of the rubber foam becomes hard, which is not preferable. On the other hand, if it exceeds 90 parts by weight, the stability is lowered in the concentration step for increasing the solid content concentration of the copolymer latex. Preferably it is 55-80 weight part, More preferably, it is 58-75 weight part.
[0016]
If the vinyl cyanide monomer is less than 10 parts by weight, the stability is lowered in the concentration step for increasing the solid content concentration of the copolymer latex. On the other hand, if it exceeds 40 parts by weight, the texture of the rubber foam becomes hard, which is not preferable. Preferably it is 20-40 weight part, More preferably, it is 25-40 weight part.
[0017]
If the total of other copolymerizable monomers exceeds 20 parts by weight, the texture of the rubber foam becomes hard, which is not preferable. Preferably it is 0-15 weight part, More preferably, it is 0-10 weight part.
[0018]
  The rosin soap contained in the copolymer latex of the present invention is a rosin soap obtained by neutralizing rosin with an alkali such as lithium hydroxide, sodium hydroxide, potassium hydroxide or ammonia, and one or two of them. The above can be used.
  Rosin soap is 100 parts by weight of copolymer latex (in terms of solid content)0.3-3.5It must be included in parts by weight.
  Rosin soap0.3If the amount is less than parts by weight, the time from the addition of the gelling agent to the completion of gelation after foaming, that is, the gelation time becomes too long. Is not preferable because the fineness of the rubber foam is lost. Also, rosin soap3.5If the amount exceeds 50 parts by weight, handling problems may occur during the production of the copolymer latex, particularly in the concentration step. PreferablyIs 0. 5 to 3.0 parts by weight.
[0019]
  The fatty acid soap contained in the copolymer latex of the present invention refers to palmitic acid, oleic acid, linoleic acid, linolenic acid, stearic acid, tallow acid, etc., alkali such as lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Fatty acid soap neutralized with ammonia, and one or more of these can be used. Of these, fatty acid soaps made from oleic acid, linoleic acid, and beef tallow acid are particularly preferred in terms of ease of use.
  Fatty acid soap is 100 parts by weight of copolymer latex (in terms of solid content)0.3-3.5It must be included in parts by weight.
  Fatty acid soap0.3Less than parts by weight is not preferable because the expansion ratio decreases. Fatty acid soap3.5If the amount exceeds 50 parts by weight, handling problems may occur during the production of the copolymer latex, particularly in the concentration step. PreferablyIs 0. 5 to 3.0 parts by weight.
[0020]
  As described above, the amount of rosin soap and fatty acid soap contained in the copolymer latex of the present invention is limited in order to achieve the object of the present invention.At least one of rosin soap and fatty acid soap,Add as emulsifier at the start of emulsion polymerization and / or during polymerizationTo do.AlsoThe otherFurther, it may be added after completion of the polymerization reaction. Furthermore, the copolymer latex may be added before and after the step of concentrating the target solid content concentration to 60% by weight or more.
[0021]
The copolymer latex in the present invention can be produced by a known emulsion polymerization method. In the polymerization of these copolymer latexes, the above rosin soap, fatty acid soap and other emulsifiers, chain transfer agents, A polymerization initiator, a reducing agent, an electrolyte, a polymerization accelerator, a chelating agent, etc., and further a hydrocarbon solvent can be used. Moreover, there is no restriction | limiting in particular about the addition method of each monomer used at the time of superposition | polymerization, and another additive, Any of a batch addition method, a division addition method, a continuous addition method, etc. are employable.
In order to fully exhibit the effects of the present invention, the amount of emulsifiers other than rosin soap and fatty acid soap used in the emulsion polymerization of the copolymer latex is 2 weights per 100 parts by weight of the copolymer latex (in terms of solid content). It is preferable to be limited to less than or equal to parts.
[0022]
As emulsifiers other than the above rosin soap and fatty acid soap, sodium salt of naphthalene sulfonic acid formalin condensate, sulfate ester salt of higher alcohol, alkyl benzene sulfonate, alkyl diphenyl ether sulfonate, aliphatic sulfonate, nonionic surface activity Nonionic surfactants such as anionic surfactants such as sulfuric acid ester salts of polyethylene or alkyl ester type, alkyl phenyl ether type, alkyl ether type of polyethylene glycol, and the like, and one or more of these should be used Can do. In particular, sodium salt of alkylphthalene sulfonate and alkylbenzene sulfonate are preferable.
[0023]
Examples of the chain transfer agent that can be used for emulsion polymerization of the copolymer latex in the present invention include n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan. Xanthogen compounds such as alkyl mercaptan, dimethyl xanthogen disulfide, diisopropyl xanthogen disulfide, α-methylstyrene dimer, terpinolene, and thiuram compounds such as tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, 2,6- Phenolic compounds such as di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane, di Lomomethane, halogenated hydrocarbon compounds such as carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycol An acid, thiomalic acid, 2-ethylhexyl thioglycolate, etc. are mentioned, These can be used 1 type or 2 or more types. The amount of these chain transfer agents is not particularly limited, but is usually 0 to 5 parts by weight with respect to 100 parts by weight of the monomer.
[0024]
Examples of the polymerization initiator used in the emulsion polymerization of the copolymer latex in the present invention include water-soluble polymerization initiators such as potassium persulfate, sodium persulfate, and ammonium persulfate, cumene hydroperoxide, benzoyl peroxide, and t-butyl. Oil-soluble polymerization initiators such as hydroperoxide, acetyl peroxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide can be used as appropriate. In particular, use of water-soluble polymerization initiators such as potassium persulfate and sodium persulfate and oil-soluble polymerization initiators such as cumene hydroperoxide is preferable.
[0025]
In addition, it is preferable that a reducing agent is present together with the polymerization initiator in the reaction system because the reaction rate is accelerated without a decrease in performance. The kind of the reducing agent is not particularly limited, but it is generally not preferable to use a reducing agent containing a transition metal such as iron because the heat discoloration performance of the cosmetic puff is generally lowered. Even if a reducing agent containing a transition metal is used, it is surmised that the heat discoloration performance of the cosmetic puff is slightly improved if a metal sealant is added to the latex, but a reducing agent containing a transition metal such as ferrous sulfate It is better to avoid using.
Specific examples of the reducing agent preferably used in the present invention include sulfite, bisulfite, pyrosulfite, nitrite, nithionate, thiosulfate, formaldehyde sulfonate, benzaldehyde sulfonate, and the like. And carboxylic acids such as L-ascorbic acid, tartaric acid and citric acid, reducing sugars such as dextrose and saccharose, and amines such as dimethylaniline and triethanolamine. Particularly preferred are sodium sulfite, sodium formaldehyde sulfonate, and L-ascorbic acid.
[0026]
In the polymerization, saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane and cycloheptane, and unsaturated hydrocarbons such as pentene, hexene, heptene, cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene and 1-methylcyclohexene. Hydrocarbon compounds such as aromatic hydrocarbons such as benzene, toluene and xylene may be used. In particular, cyclohexene and toluene, which have a moderately low boiling point and can be easily recovered and reused by steam distillation after the completion of polymerization, are suitable from the viewpoint of environmental problems, although they are different from the object of the present invention.
[0027]
The solid content concentration of the copolymer latex of the present invention needs to be 60% by weight or more. Less than 60% by weight is not preferable because the fineness of the rubber foam is inferior.
[0028]
In order to increase the solid content concentration of the copolymer latex to 60% by weight or more, a method of concentrating the copolymer latex obtained by emulsion polymerization, and a part or all of the obtained copolymer latex particles In accordance with a known particle enlargement method, for example, a copolymer latex having an average particle size of 50 nm to 200 nm is enlarged to 100 nm to several microns, and then concentrated to a solid content concentration of 60% by weight or more. Although it is possible to adjust, the latter method is particularly preferable from the viewpoint of easy adjustment.
If the solid content concentration of the copolymer latex is less than 60% by weight, the texture of the cosmetic puff becomes coarse and the texture becomes hard, which is not preferable. Preferably it is 63 weight%, More preferably, it is 65 weight% or more.
[0029]
The method for enlarging the particle size of the copolymer latex is not particularly limited. For example, a method of adding a particle size thickening agent such as carboxyl group-containing copolymer particles and forcibly stirring (generally chemical agglomeration). A method in which the reaction is stopped in the middle of the polymerization and the particles swell with the monomer and are forcibly stirred in a state where they are easily fused to each other. The styrene is added to the copolymer latex after the completion of the polymerization. A monomer latex such as toluene, cyclohexene, etc., and the particles are swollen with them and forcibly stirred in a state where they are easily fused to each other, a copolymer latex heated to a certain temperature Examples thereof include a method of enlarging by applying high shear by spraying from a nozzle at a constant pressure (hereinafter referred to as warming and pressure enlargement method).
[0030]
The copolymer latex for rubber foam according to the present invention is required to contain a specific amount of fatty acid soap and rosin soap with respect to the monomer composition and the copolymer latex. It is also possible to blend two types of copolymer latex, in which case the composition of the finally obtained copolymer latex, the content of fatty acid soap and rosin soap are within the range specified in the present invention. It may be adjusted so that
[0031]
The specific method of each step in the method for producing a rubber foam using the copolymer latex of the present invention is not particularly limited, and any conventionally known method can be used. The rubber foam production process usually consists of a process of adding a vulcanizing agent and an auxiliary agent, a foaming process, a gelling process, a vulcanizing process, a washing process, and a drying process. In the step of adding a vulcanizing agent and an auxiliary agent, an auxiliary agent such as a vulcanizing agent, a vulcanization accelerator, and an anti-aging agent, a thickener, a water retention agent, and a coloring agent are added as necessary. The vulcanizing agent is not particularly limited. For example, sulfur or colloidal sulfur obtained by emulsifying and dispersing it is used. Vulcanization aids and vulcanization accelerators are not particularly limited. Examples of vulcanization aids include zinc white, and examples of vulcanization accelerators include dithiocarbamate accelerators such as zinc diethyldithiocarbamate, 2-mercapto. Examples include thiazole accelerators such as benzothiazole and its zinc salt and dibenzothiazyl disulfide.
[0032]
In the production of the rubber foam, the addition amount of each of the above-mentioned agents with respect to 100 parts by weight in terms of solid content of the copolymer latex of the present invention is not particularly limited. For example, sulfur 0.3 to 6 parts by weight, zinc white A range of 0.5 to 7 parts by weight and a vulcanization accelerator of 0.2 to 4 parts by weight is common. Moreover, you may add auxiliary agents, such as various anti-aging agents, a thickener, a water retention agent, and a coloring agent, as an auxiliary agent in the range which does not prevent the effect of this invention.
[0033]
Any conventionally known method can be used as the foaming method in the production of the rubber foam, and it is not particularly limited.
As the foaming method, a forced foaming method alone in which air is mixed by various methods, or a gas generating substance can be used in combination by the forced foaming method. As the forced foaming device, for example, an Oaks foaming machine, an ultrasonic foaming machine or the like can be used.
[0034]
Any conventionally known method can be used for the gelation method and is not particularly limited, and a thermal coagulation method using an organopolysiloxane or a freezing coagulation method for rapidly lowering the temperature can also be used. It is considered that the room temperature coagulation method (Dunlop method), which is added to a copolymer latex foamed with a silicon fluoride compound such as sodium silicofluoride, potassium silicofluoride or sodium titanium silicofluoride as a gelling agent, is considered most effective. In addition, the copolymer latex of the present invention can provide a gel time suitable for stably producing a fine rubber foam.
[0035]
Various conditions in the vulcanization step after gelation are not particularly limited, and a good quality rubber foam can be obtained by vulcanization at a temperature of about 100 to 150 ° C. for about 10 to 100 minutes. There are no particular restrictions on the conditions of the washing process and drying process, but washing with water or hot water at 25 to 60 ° C. for 5 to 20 minutes with stirring, and then water is removed by a method such as a centrifugal separation method. It is dried at a temperature of about 40 to 120 ° C. so that the texture of the foam can be maintained.
In order to obtain a final molded product such as a cosmetic puff product from the rubber foam that has been finished up to the drying step, the rubber foam is cut into a predetermined thickness, cut into a predetermined shape, and the cut side surfaces and edges are cut off. Polish with a fine rotating grindstone.
[0036]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to these Examples, unless the summary is exceeded. In the examples, parts and percentages indicating percentages are based on weight unless otherwise specified. However, the components other than pure water and water indicate the solid content or the weight part or weight% of the active ingredient. In addition, various physical properties in the examples were evaluated by the following methods.
[0037]
Determination of gelling properties
2 parts of colloidal sulfur as a vulcanizing agent and 1.5 parts of zinc diethyldithiocarbamate (Noxeller EZ manufactured by Ouchi Shinsei Chemical Co., Ltd.) Add 3 parts of flower and mix thoroughly. Next, 200 ml is placed in a transparent 2000 ml cylindrical container with a mark line at 1400 ml, and is forcibly stirred at room temperature using a twin-screw hand mixer. By volume until the upper part of the foam surface reaches the mark line. 7 times foam. Then, 2 parts of sodium silicofluoride slurry was added, and stirring was continued for 30 seconds at room temperature. The mixture was poured into a mold, and the upper part of the foamed liquid surface was lightly pressed with fingers at intervals of 30 seconds, and gelation stopped flowing. Determine if the end point has been reached. The time from the addition time of sodium silicofluoride to the gelation end point was defined as the gelation time, and the quality of the gelation characteristics was determined as follows.
Gelation time within 1 minute: Impossible (1) (Mold flowability is poor and cannot be molded)
Gelation time 1 minute or more and less than 2 minutes: Possible (1) (lower limit for maintaining mold flow)
Gelation time from 2.0 minutes to 5.0 minutes: good (excellent mold flow and maintain foamed state)
Gelation time: 5.0 minutes or more and 5.5 minutes or less: Possible (2) (There is a possibility that some bubbles break in the gelation process)
Gelation time of 5.5 minutes or more: Impossible (2) (The gelation process is too long and there is a high possibility of bubble breakage)
[0038]
Evaluation of foaming properties
200 ml of the copolymer latex is put into the cylindrical container described above, and the stopwatch is started and at the same time forcedly stirred at room temperature using a biaxial hand mixer until the upper part of the foam surface reaches the mark line, that is, 7 by volume. Lap time is measured for double foaming. When foaming 7 times, stirring was stopped, and then the foamed state was observed with the naked eye for 5 minutes, and judged as follows.
Impossible (1): Foaming ratio does not reach 7 times even after stirring for 5 minutes.
Impossible {circle around (2)}: The foaming ratio reaches 7 times within 5 minutes from the start of stirring, but obvious bubble breakage and a decrease in foaming ratio are observed within 5 minutes after the stirring is stopped.
Possible: The expansion ratio reaches 7 times within 5 minutes from the start of stirring. Slight bubble breakage is observed within 5 minutes after the stirring is stopped, but no reduction in the expansion ratio is observed.
Good: The expansion ratio reaches 7 times within 2 minutes to 5 minutes from the start of stirring. Within 5 minutes after the stirring is stopped, neither bubble breakage nor reduction in the expansion ratio is observed.
Excellent: The expansion ratio reaches 7 times in less than 2 minutes from the start of stirring. Within 5 minutes after the stirring is stopped, neither bubble breakage nor reduction in the expansion ratio is observed.
[0039]
Molding of rubber foam
2 parts of colloidal sulfur as a vulcanizing agent and 1.5 parts of zinc diethyldithiocarbamate (Noxeller EZ manufactured by Ouchi Shinsei Chemical Co., Ltd.) Add 3 parts of flower and force-stir at room temperature using a biaxial hand mixer to foam 7 times in volume as described above. Thereafter, 2 parts of a slurry of sodium silicofluoride was added, stirring was continued for 30 seconds at room temperature, and the mixture was poured into a mold for molding. After gelation, the slurry was vulcanized with 110 ° C. pressurized steam for 40 minutes. The rubber foam taken out from the mold was sliced to a thickness of 1 cm in the length direction, washed with hot water at 60 ° C. for 10 minutes, and then dried in an oven at 70 ° C. for 90 minutes to obtain a rubber foam molded product.
[0040]
Quality evaluation of rubber foam
The fineness, elasticity, and texture of the molded rubber foam molded product as described above were sensuously inspected and determined as follows.
Defect (1): The foamed structure is rough, the texture is hard, and the elasticity is insufficient.
Defect (2): The texture of the foam structure is fine, but the texture is hard and the elasticity is insufficient.
Good (1): The texture of the foam structure is fine, but the texture is slightly hard and the elasticity is slightly inferior.
Good (2): The texture is soft and rich in elasticity, but the texture of the foam structure is slightly rough.
Excellent: The texture of the foam structure is fine, the texture is soft, and the elasticity is high.
[0041]
Measurement of average particle size of copolymer latex
After dyeing the copolymer latex with osmium tetroxide, a transmission electron micrograph was taken, the diameter of 1000 particles was measured, and the number average particle diameter was determined.
[0042]
Preparation of copolymer latex A
In a pressure-resistant 20-liter polymerization reactor, 105 parts of pure water, 1.5 parts of potassium oleate as an emulsifier, 1 part of a sodium salt of a naphthalene sulfonic acid formalin condensate, 0.3 part of sodium formaldehyde sulfonate, 67 parts of butadiene, Acrylonitrile (33 parts), t-dodecyl mercaptan (1 part), and cyclohexene (0.5 part) were charged, and the temperature was maintained at 22 ° C. while stirring. Next, 0.15 part of cumene hydroperoxide was added to initiate the reaction. Next, when the polymerization conversion reached 25%, 0.3 part of potassium oleate, 0.05 part of sodium formaldehydesulfonate and 2 parts of pure water were added. Next, when the polymerization conversion reached 50%, 0.3 part of potassium oleate, 0.05 part of sodium formaldehydesulfonate and 2 parts of pure water were added. Next, when the polymerization conversion reached 75%, 0.3 part of potassium oleate, 0.05 part of sodium formaldehydesulfonate and 2 parts of pure water were added. When the polymerization conversion rate reached 95% or more, diethylhydroxyamine was added as a polymerization terminator to complete the polymerization. Next, residual butadiene was removed by steam distillation to obtain a copolymer latex A. The solid content concentration of the copolymer latex A was 40%, and the average particle size was 120 nm.
[0043]
Preparation of copolymer latex B
In a pressure-resistant 20-liter polymerization reactor, 110 parts of pure water, 1.8 parts of potassium rosinate as an emulsifier, 0.7 parts of sodium salt of formalin condensate of naphthalene sulfonic acid, 0.3 part of sodium formaldehyde sulfonate, 63 parts of butadiene Part, acrylonitrile 37 parts, t-dodecyl mercaptan 0.7 part, α-methylstyrene dimer 0.2 part, and the temperature was kept at 27 ° C. with stirring. Next, 0.12 parts of cumene hydroperoxide was added to initiate the reaction. Subsequently, when the polymerization conversion reached 25%, 0.2 parts of potassium rosinate, 0.05 parts of sodium formaldehydesulfonate, and 2 parts of pure water were added. Next, when the polymerization conversion reached 50%, 0.2 parts of potassium rosinate, 0.05 parts of sodium formaldehyde sulfonate and 2 parts of pure water were added. Next, when the polymerization conversion reached 75%, 0.2 parts of potassium rosinate, 0.05 parts of sodium formaldehydesulfonate, and 2 parts of pure water were added. When the polymerization conversion rate reached 95% or more, diethylhydroxyamine was added as a polymerization terminator to complete the polymerization. Next, residual butadiene was removed by steam distillation to obtain a copolymer latex B. The solid content concentration of the copolymer latex B was 39%, and the average particle size was 115 nm.
[0044]
Preparation of copolymer latex C
In a pressure-resistant 20-liter polymerization reactor, 105 parts of pure water, 1 part of sodium rosinate as an emulsifier, 1 part of potassium oleate, 0.5 part of sodium salt of formalin naphthalene sulfonate, 0.3 part of sodium formaldehyde sulfonate Parts, butadiene 60 parts, acrylonitrile 35 parts, butyl acrylate 5 parts and t-dodecyl mercaptan 1.2 parts were charged, and the temperature was maintained at 15 ° C. while stirring. Next, 0.15 part of cumene hydroperoxide was added to initiate the reaction. Next, when the polymerization conversion reached 25%, 0.2 parts of sodium rosinate, 0.05 parts of sodium formaldehyde sulfonate and 2 parts of pure water were added. Next, when the polymerization conversion reached 50%, 0.2 part of potassium oleate, 0.05 part of sodium formaldehydesulfonate and 2 parts of pure water were added. Next, when the polymerization conversion reached 75%, 0.2 part of potassium oleate, 0.05 part of sodium formaldehydesulfonate, and 2 parts of pure water were added. When the polymerization conversion rate reached 95% or more, diethylhydroxyamine was added as a polymerization terminator to complete the polymerization. Next, residual butadiene was removed by steam distillation to obtain a copolymer latex C. The solid content concentration of the copolymer latex C was 40%, and the average particle size was 104 nm.
[0045]
Preparation of copolymer latex D
The same procedure as for the copolymer latex C was used, except that the amount of monomer and t-dodecyl mercaptan was changed to 45 parts butadiene, 45 parts acrylonitrile, 10 parts methylmethacrylate, and 0.6 parts t-dodecyl mercaptan. Copolymer latex D was obtained. The solid content concentration of the copolymer latex D was 41%, and the average particle size was 125 nm.
[0046]
Preparation of copolymer latex E
A copolymer latex E was obtained in the same manner as for the copolymer latex C except that the amounts of the monomer and t-dodecyl mercaptan were changed to 91 parts of butadiene, 9 parts of acrylonitrile, and 2 parts of t-dodecyl mercaptan. The solid content concentration of the copolymer latex E was 40%, and the average particle size was 98 nm.
[0047]
Preparation of copolymer latex A1
The copolymer latex A was subjected to a temperature of 48 ° C. and a pressure of 3.3 × 10 using a Manton-Gaulin homogenizer.⁶After carrying out the particle diameter enlargement process by the heating pressurization enlargement method of the conditions of Pa, it concentrated and obtained copolymer latex A1. The solid content concentration was 65%, and the average particle size was 650 nm.
[0048]
Preparation of copolymer latex B1
The copolymer latex B was subjected to a particle size enlargement treatment by a heating and pressure enlargement method under the same conditions as the copolymer latex A1, and then concentrated to obtain a copolymer latex B1. The solid content concentration was 66%, and the average particle size was 700 nm.
[0049]
Preparation of copolymer latex D1
A copolymer latex D1 was obtained by subjecting the copolymer latex D to a particle size enlargement treatment by the heating and pressure enlargement method under the same conditions as the copolymer latex A1, and then concentrating. The solid content concentration was 66%, and the average particle size was 510 nm.
[0050]
Preparation of copolymer latex E1
The copolymer latex E was subjected to a particle diameter enlargement process by the heating and pressure enlargement method under the same conditions as the copolymer latex A1, but the copolymer latex aggregated when the solid content concentration exceeded 58%. Copolymer latex E1 was not obtained.
[0051]
Preparation of copolymer latex A2
After adding 1.5 parts of potassium rosinate to 100 parts in terms of solid content of the copolymer latex A, the particle diameter is enlarged by the heating and pressure enlargement method under the same conditions as the copolymer latex A1. And concentrated to obtain copolymer latex A2. The solid content concentration was 66%, and the average particle size was 610 nm.
[0052]
Preparation of copolymer latex B2
After adding 1.5 parts of sodium oleate to 100 parts in terms of solid content of copolymer latex B and subjecting it to particle diameter enlargement treatment by heating and pressure enlargement method under the same conditions as copolymer latex A1 And concentrated to obtain a copolymer latex B2. The solid content concentration was 65%, and the average particle size was 560 nm.
[0053]
Preparation of copolymer latex C1 and C2
The copolymer latex C was subjected to a particle size enlargement treatment by the heating and pressure enlargement method under the same conditions as the copolymer latex A1, and then concentrated to obtain a copolymer latex C2. The solid content concentration was 67%, and the average particle size was 740 nm. Moreover, copolymer latex C1 was obtained in the middle of the concentration process of copolymer latex C2. The solid content concentration was 57%, and the average particle size was 720 nm.
[0054]
Preparation of copolymer latex blend A1 / B
Copolymer latex A1 / copolymer latex B was blended to a solid content conversion ratio of 70 parts / 30 parts, and concentrated to obtain copolymer latex blend A1 / B. The solid content concentration was 67%, and the average particle size was 490 nm.
[0055]
Preparation of copolymer latex blend A / B1
Copolymer latex A / copolymer latex B1 was blended so that the copolymer component ratio was 30 parts / 70 parts, and concentrated to obtain copolymer latex blend A / B1. The solid content concentration was 67%, and the average particle size was 540 nm.
[0056]
Table 1 shows polymerization prescriptions of the above copolymer latexes A to E.
Moreover, the evaluation of gelation characteristics, foaming characteristics, and quality of rubber foam using the copolymer latex A1, B1, C1, D1, A2, B2, C2, A1 / B, and A / B1 after concentration are described above. Evaluation was made according to the method. The results are shown in Table 2 together with the monomer composition of each copolymer latex, the content of rosin soap and fatty acid soap, the average particle size, and the solid content concentration.
[0057]
[Table 1]

[0058]
[Table 2]

[0059]
【The invention's effect】
As described above, the present invention is a copolymer latex used for the production of a fine rubber foam excellent in the balance between elasticity and texture, and further from the foaming process to the gelation process in producing the rubber foam. It is possible to provide a rubber latex copolymer latex that enables stable and efficient production of fine rubber foam that maintains a fine foam structure and expansion ratio, and has a good balance between elasticity and texture. it can.

Claims (1)

Emulsifying monomer comprising 50 to 90 parts by weight of aliphatic conjugated diene monomer, 10 to 40 parts by weight of vinyl cyanide monomer, and 0 to 20 parts by weight of other monomers copolymerizable therewith An emulsion polymerization step of polymerizing to obtain a copolymer latex;
  Concentrating the copolymer latex to a solids concentration of 60% by weight or more;
  Addition step of adding 0.3 to 3.5 parts by weight of rosin acid soap and 0.3 to 3.5 parts by weight of fatty acid soap in terms of solid content with respect to 100 parts by weight of the copolymer latex (in terms of solid content) And
  In the emulsion polymerization step, the rosin acid soap and / or the fatty acid soap is added. A method for producing a copolymer latex for a rubber foam.