JPH0218682B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Fields This invention is a latex with excellent chemical stability.
The present invention also relates to a method for producing a vinylidene chloride copolymer latex whose coating film has excellent light coloring resistance and gas barrier properties. BACKGROUND ART It is known that vinylidene chloride copolymers are colored due to loss of thermal stability and photostability when metals or their ions are present in the copolymer. Therefore, for vinylidene chloride copolymer raw material for melt extrusion, which requires heat resistance and light stability,
Efforts are being made to avoid contamination with metals and their ions as much as possible. Further, during melt processing, a copolymer with a low melt viscosity and a small molecular weight is desirable, but a low molecular weight vinylidene chloride copolymer tends to have poor thermal stability. On the other hand, vinylidene chloride copolymer latex, which is used in the processing process without reaching a molten state by heating for drying and does not have relatively strict requirements for heat resistance stability, has traditionally been treated with anion containing metal ions. emulsifiers have been used. This is because this anionic emulsifier has excellent effects on controlling the particle size of latex and mechanical stability of latex. However, poor thermal stability is basically a major drawback, and to improve this, it is also possible to use only nonionic emulsifiers.
Shown as 14676. On the other hand, this method has a disadvantage in that a small amount of nonionic emulsifier results in poor mechanical stability of the latex, and a large amount must be used. Normally, when using an anionic emulsifier, a latex with good stability can be obtained by using an amount of 3.0 parts by weight or less per 100 parts by weight of the monomer, but in the case of a nonionic emulsifier, it is usually 5.0 parts by weight or less. It is also necessary to use a certain amount. This large amount of emulsifier significantly deteriorates the gas barrier properties of the film, especially when the latex is used by coating it on a film, etc., thereby defeating the purpose of using the vinylidene chloride copolymer. Now, in order to eliminate the above-mentioned drawbacks of using only nonionic emulsifiers and obtain the good points of using nonionic emulsifiers, such as thermal stability and chemical stability of the latex, we need to use an extremely small amount of anionic emulsifier and more than half of the amount of nonionic emulsifiers. The method of using emulsifiers was published in Japanese Patent Application Laid-Open No. 1986-
139136, JP-A-58-84842, JP-A-59-152907, etc. In these methods, the chemical stability of the latex is improved compared to the case of anionic emulsifiers, but is not sufficient.
Furthermore, the thermal stability is almost unchanged or deteriorates compared to the case of anionic emulsifiers. The present inventors have conducted extensive research into this difficult problem, and have attempted to obtain a latex that is made of a vinylidene chloride copolymer that has excellent thermal stability, photocoloring stability, and gas barrier properties, and also has excellent chemical stability. This led to the completion of the present invention. Summary of the Invention That is, the present invention provides the following methods: 1. 100 parts by weight of a monomer mixture consisting of 60 to 94% by weight of vinylidene chloride and 6 to 40% by weight of a monomer copolymerizable with vinylidene chloride, and an anionic emulsifier.
0.03~1.0 parts by weight and 0.1~ nonionic emulsifier
When carrying out emulsion polymerization in the presence of a polymerization initiator and an emulsifier mixture in which the nonionic emulsifier accounts for 60 parts by weight or more of the total emulsifier, the emulsifier accounts for 20 parts by weight or less of 100 parts by weight of the monomer mixture. Not more than 25% by weight of the mixture and 30% of the polymerization initiator
After carrying out emulsion polymerization in advance using % by weight or less, 80% by weight or more of the monomer mixture is added continuously and uniformly, and during the period of continuous addition, 75% by weight or more of the emulsifier mixture and The emulsifier extraction rate from the copolymer with methanol is characterized by continuously and uniformly adding all or a portion of the remaining polymerization initiator to 50% of the emulsifier used.
% or less by weight of vinylidene chloride copolymer latex. 2. A patent in which the monomer mixture consists of 60-94% by weight of vinylidene chloride, 0.5-10% by weight of methacrylonitrile or acrylonitrile, 0.5-5% by weight of glycidyl methacrylate, and 0-25% by weight of a monomer copolymerizable with these. A method for producing a vinylidene chloride copolymer latex according to claim 1. It is related to. In the present invention, during emulsion polymerization of a monomer mixture containing vinylidene chloride as a main component, an emulsifier mixture and a polymerization initiator are added continuously and uniformly in a constant ratio and in a constant amount during the continuous addition period of the monomer mixture. According to the present invention, which is an emulsion polymerization method, a latex containing a vinylidene chloride copolymer having a specific molecular weight (ηsp/c) and a low amount of emulsifier extraction can be produced. By this method, a latex that is chemically stable against cationic emulsifiers and electrolytes can be obtained despite the extremely small amount of emulsifier, and the copolymer coating film obtained by applying this latex is Even though it contains an anionic emulsifier, it has good light resistance and gas barrier properties, making it extremely useful for packaging tobacco, foods, etc. DETAILED DESCRIPTION OF THE INVENTION The monomer mixture used in the present invention contains vinylidene chloride in an amount of 60 to 94% by weight, preferably 75 to 93% by weight.
It consists of 6 to 40% by weight, preferably 7 to 25% by weight of a monomer copolymerizable with vinylidene chloride. If vinylidene chloride is less than 60% by weight, the resulting copolymer will have almost no crystallinity and will have poor gas barrier properties. On the other hand, if the amount is 94% by weight or more, the copolymer becomes latex-like and crystallizes in a short period of time, which is disadvantageous because it cannot be used in applications where latex is used to form a film. Monomers copolymerizable with vinylidene chloride include methyl acrylate,
Ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate,
One or two selected from octyl acrylate, methyl methacrylate, ethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, acrylonitrile, methacrylonitrile, vinyl chloride, vinyl acetate, acrylic acid, methacrylic acid, itaconic acid, etc. More than one species can be suitably used. In the present invention, in the above vinylidene chloride mixture,
Vinylidene chloride 60-94% by weight, preferably 75-93
0.5-10% by weight of methacrylonitrile or acrylonitrile, 0.5-5% by weight of glycidyl methacrylate and 0-25% by weight of monomers copolymerizable with vinylidene chloride as mentioned above, preferably 5-15% by weight. It is particularly preferable to use a specific monomer mixture consisting of %. Methacrylonitrile or acrylonitrile has the effect of increasing the Tg of the copolymer and at the same time increasing the cohesive force of the copolymer due to its -CN group.
Gas barrier properties can be further improved. However, if the amount is too large, the copolymer
The Tg becomes high, making it unsuitable for use in forming latex films. Glycidyl methacrylate has an epoxy group in its chemical structure, which is effective for improving the thermal stability of vinylidene chloride copolymers. However, if the amount is too large, crosslinking occurs and the latex particles harden, which is still inconvenient for use in forming latex films. Furthermore, when glycidyl methacrylate is used, it is not preferable to use a large amount of ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid because they may cause a crosslinking reaction. In the case of a monomer mixture containing methacrylonitrile or acrylonitrile and glycidyl methacrylate in the above range, a coating film particularly excellent in both gas barrier properties and light coloring resistance can be obtained. As for the emulsifier used in polymerization, the anionic emulsifier is in the range of 0.03 to 1.0 parts by weight per 100 parts by weight of the total monomers, and the smaller the amount as much as possible while maintaining the stability of the latex during polymerization, the better the copolymer. Desirable to prevent deterioration of thermal stability. That is, if the amount is less than 0.03 parts by weight, the stability of the latex will be impaired, so it is necessary to increase the amount of the nonionic emulsifier. As will be described later, this method is undesirable in terms of gas barrier properties. On the other hand, if it exceeds 1.0 parts by weight, the thermal stability of the copolymer will deteriorate. The nonionic emulsifier is used in an amount of 0.1 to 1.5 parts by weight, preferably as little as possible while maintaining the stability of the latex. On the other hand, if it exceeds 1.5 parts by weight, the gas barrier properties of the copolymer tend to deteriorate. As the emulsifier, an anionic emulsifier and a nonionic emulsifier are mixed in amounts within the above range, and the nonionic emulsifier in the mixture is 60% by weight.
When used within the above range, the stability of the latex and the thermal stability of the copolymer reach a satisfactory level. Examples of anionic emulsifiers include alkyl sulfate salts, alkylbenzene sulfonate salts,
Alkylnaphthalene sulfonate, dialkyl sulfosuccinate, alkyl phosphate, naphthalene sulfonic acid formalin sulfonic acid condensate, polyoxyethylene alkyl sulfate, alkyl diphenyl ether disulfonate, alkyl sulfonate, vinyl sulfone Acid salts, styrene sulfonates, etc. can be used. As the nonionic emulsifier, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, etc. can be used, and those having an HLB in the range of 7 to 20 are easily used. Next, as a polymerization initiator, water-soluble inorganic peroxides, organic peroxides, and organic peroxides that are even slightly soluble in water can be used, and in some cases, these may also be used. Can be used as a redox initiator in combination with a reducing agent. As the inorganic peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, etc. can be used. Examples of organic peroxides include t-butyl hydroperoxide, succinic acid peroxide, t-butyl peroxymaleic acid, cumene hydroperoxide,
etc. can be used. Furthermore, water-soluble azo compounds such as 2,2'-azobis(2-amidenopropane) hydrochloride can also be used. Reducing agents used in combination with these peracids include sodium bisulfite,
Longalitz salt, oxalic acid, maleic acid, paraoxybenzoic acid, thiourea, ascorbic acid, etc. are used. The amount of polymerization initiator used varies depending on the molecular weight of the desired copolymer, but usually
It is preferably 0.02 to 0.2 parts by weight per 100 parts by weight. Further, all or at least a portion of the polymerization initiator is necessarily added during the period in which the monomer mixture is continuously added.
Continuous addition is necessary. Next, a specific method of emulsion polymerization of the present invention will be explained. In the present invention, a pressure-resistant container containing deionized water is
(1) The entire amount of the monomer mixture, emulsifier mixture, and initiator may be added continuously and uniformly from the start of polymerization, or (2) the monomer mixture, emulsifier mixture,
After adding a portion of the polymerization initiator and polymerizing to some extent, the remaining monomer mixture, emulsifier mixture, and polymerization initiator may be added continuously and uniformly. The emulsifier and polymerization initiator are preferably added in the form of an aqueous solution. In the case of (2) above, a small amount of the monomer mixture, emulsifier mixture, and polymerization initiator are added to water in advance to carry out emulsion polymerization (so-called seed polymerization), but the amount of each is equal to the total amount of the monomer mixture. is preferably 20% by weight or less, the emulsifier is 25% by weight or less, and the polymerization initiator is preferably less than 30% by weight.
That is, at least 80% by weight of the monomer mixture is continuously added to the emulsifier mixture.
It is necessary that 75% by weight or more and part of the polymerization initiator are simultaneously and continuously added. The compositions of the monomer mixture and emulsifier mixture during continuous addition may be always the same or different. In the case of (2), the monomer mixture used in advance polymerization,
The composition of the emulsifier mixture may also be the same as during continuous addition or may be different. In (1) and (2), (2)
This is preferable because the number of polymer particles becomes constant and the particle size can be easily controlled. In emulsion polymerization, if the dielectric number is constant, the polymerization rate is proportional to the monomer concentration in the polymer particles, and the average degree of polymerization (molecular weight) is proportional to the monomer concentration in the polymer particles.
It is inversely proportional to the rate of radical penetration into particles. Therefore, the monomer concentration in polymer particles and the rate of radical penetration into the particles are important factors governing the polymerization rate, average degree of polymerization, and degree of polymerization distribution in emulsion polymerization. In the present invention, during the continuous addition of the monomer mixture,
By simultaneously and continuously adding and polymerizing an emulsifier mixture and a polymerization initiator, the polymerization rate, average degree of polymerization, and degree of polymerization distribution are made uniform, thereby achieving the desired purpose. For example, during polymerization, if more than the entire monomer mixture or more than 20% by weight is added at once, the present invention not only fails to maintain the stability of the latex due to the small amount of emulsifier and initiator, but also causes the polymerization reaction to deteriorate. It is difficult to proceed. Continuous addition of monomers is not only effective in controlling the monomer concentration within the polymer particles, but also provides uniform copolymerization, especially in copolymerization between monomers with widely different copolymerization reactivity ratios. It is also effective for obtaining a copolymer having a specific composition. In addition, if the emulsifier is added in the entire amount or more than 25% by weight at the beginning, or if the remaining amount is added in the middle of polymerization,
Not only is polymerization delayed, but the chemical stability of the latex is degraded, and as will be described later, the amount of methanol extracted is increased, resulting in a decrease in thermal stability. The presence of a large amount of emulsifier ultimately inhibits chemical stability by increasing the number of polymer particles, but on the other hand, it temporarily adsorbs closely to the surface of the polymer particles, reducing the rate of monomer penetration and It is thought that the radical penetration rate decreases, which adversely affects the polymerization rate and degree of polymerization. For this reason, it is extremely important to ensure that the amount of emulsifier adsorbed to latex particles is uniform during polymerization, as well as to uniformly add monomers and initiators, in order to control the polymerization rate and degree of polymerization. be. As a guideline for uniform addition of the emulsifier, it is desirable to maintain the surface tension of the latex constant. On the other hand, if the entire amount or more than half of the polymerization initiator is added at once at the start of polymerization, the degree of polymerization of the copolymer formed at the initial stage of polymerization will decrease, which will not only deteriorate the thermal stability of the copolymer but also cause problems in the latter half of polymerization. However, this method has the disadvantage that the polymerization reaction is delayed. In addition, it is also a preferable method to have a reducing agent present in the polymerization system so that the added initiator immediately becomes radicals and the radical concentration remains constant during the polymerization in order to obtain a uniform polymerization rate and degree of polymerization. . Also, after the continuous addition of the monomer mixture, a polymerization initiator can be added to complete the polymerization. Thus, in the present invention, it is essential to add the monomer mixture, emulsifier mixture, and initiator simultaneously, continuously and uniformly to the polymerization system. Here, uniformly adding means adding a substantially constant amount within the same time, that is, adding at a substantially constant rate. The degree of polymerization or molecular weight of the copolymer obtained in the present invention is expressed in terms of solution viscosity, ηsp/c=0.035 to
0.075/g (ηsp: specific viscosity, c: solution concentration), more preferably 0.04 to 0.07/g.
If it is lower than 0.035, the thermal stability and light coloring resistance will be extremely poor, while if it exceeds 0.075, it will become difficult to melt and the heat sealing property will deteriorate. In particular, if the contact time with the hot plate during heat sealing is less than 0.5 seconds, the heat sealing properties will deteriorate significantly. In the present invention, the continuous addition amounts of the monomer mixture, initiator, and emulsifier are adjusted so that the degree of polymerization falls within this range. Additionally, the polymerization temperature can also be determined accordingly. However, generally the polymerization temperature is 30~
70°C is preferred. Note that the solution viscosity was calculated by measuring the solution viscosity of 4 g/solution of cyclohexanone at 30°C. Furthermore, in the present invention, by simultaneously and continuously adding a monomer mixture, an emulsifier mixture, and a polymerization initiator to the polymerization system, surprisingly, most of the emulsifiers, especially nonionic emulsifiers, are converted into copolymers by methanol extraction. It was found that the methanol extraction rate was only less than 50% of the total emulsifier used. As a result, the chemical stability of the latex of the present invention is extremely superior to latexes obtained with conventional mixtures of anionic emulsifiers and nonionic emulsifiers. Although the detailed reasons for this finding confirmed by the present inventors will have to wait for future research, the simultaneous and continuous addition of the monomers, initiators, and emulsifiers described above can be especially helpful in starting It is presumed that the nonionic emulsifier is grafted onto the copolymer because agent radicals are constantly generated in water. Due to this unique form of existence of nonionic emulsifiers, despite the presence of both nonionic emulsifiers and anionic emulsifiers, there is no deterioration in thermal stability caused by anionic emulsifiers, and relatively large amounts of nonionic emulsifiers are present. Even when a synthetic emulsifier is used, the gas barrier properties are not deteriorated, and together with the small amount of total emulsifier, it is thought that the thermal stability and gas barrier properties of the copolymer have reached an unprecedented level. Now, latex can be obtained as described above, but the optimum particle size for latex is in the range of 800 to 2000 Å, and this particle size can be achieved by adjusting the appropriate amounts of emulsifier, initiator, and monomer at the initial stage of polymerization. can be obtained. The latex of the present invention can be used with additives such as silica, wax, and pigments, a cationic surfactant as an antistatic agent, and alcohol as a surface tension adjusting agent or antifoaming agent. Furthermore, it can be applied to paper, plastic film, etc. using a conventional coating method. The usefulness of the present invention will be explained below using Examples and Comparative Examples. The following percentages and parts are respectively weight percentages.
and parts by weight. First, the evaluation test method will be described. (1) Chemical stability of latex Latex with a solid content concentration of 50% was mixed with methanol at 20°C and an aqueous solution of a cationic surfactant with a concentration of 10% (cationic surfactant: manufactured by Lion Akzo Co., Ltd.,
One to two drops were added to each of Esocard C-12) to test whether the latex would break down (coagulate). Those that did not coagulate and were milky white were considered good. (2) Methanol extraction rate of emulsifier A latex with a solid content concentration of 50% was coated on a biaxially stretched polypropylene film (abbreviated as OPP) so that the solid content was 5 μm thick in a room at 20°C.
A dry film was formed. After drying, only the coating film was peeled off using a cellophane adhesive tape, and approximately 10 g of the coating film was cut into strips and extracted with methanol solvent using a Soxhlet extractor for 50 hours. The extraction amount was measured once at 40 hours, and the amount confirmed to be constant after 50 hours is shown. However, if the constant weight was not reached even after 50 hours, measurements were carried out in 10 hour increments and extraction was continued until the constant weight was reached. The methanol extraction rate is expressed as a percentage of the amount of emulsifier extracted relative to the total emulsifier used. (3) Molecular weight After freezing and coagulating the latex, it was washed with methanol and dried in a vacuum dryer to obtain a powder. This powder sample was dissolved in cyclohexanone at a concentration of 4 g/ml, and the viscosity of the solution was measured at 30°C.
ηsp/c was calculated. (4) Oxygen permeability: Urethane resin adhesives “Takerak A-310” and “Takenate A-3” (Takeda Pharmaceutical Co., Ltd.) were applied as anchor coating agents (abbreviated as AC) to the OPP corona-treated surface with a thickness of 20 μm. 15:1
The mixture was mixed at a ratio of 0.3 g/m ² as a solid content, and dried at 80° C. for 30 seconds. Then, immediately prepare a latex with a solid content concentration of 40% (silica powder,
Thyroid 244 (manufactured by Fuji Davison) with 0.2 parts by weight added per 100 parts by weight of resin) with a solid content of 5.0
g/m ² on the surface of the AC agent, and heated at 80℃ for 30 minutes.
Dry for seconds. After drying, it was left at 40°C for 48 hours, and then adjusted at 20°C and 90% RH for 20 hours. This sample was subjected to MOCONOX-
Measured using TRAN100 type testing machine. (5) Light coloring resistance (Since it is recognized that there is a parallel relationship with thermal stability, light coloring resistance was measured as a guideline for thermal stability.) Solid content concentration was measured on a 20 μm thick OPP corona-treated surface.
A 50% latex was applied at a solid content of 10 g/m ² and dried at 80° C. for 30 seconds. then 40
It was left at ℃ for 48 hours. Then cut into strips,
Stack 10 sheets with the coated side facing up. This strip-shaped sample is continuously exposed on a sunny day from 10 a.m. to 3 p.m. until the predetermined exposure time is reached.
The degree of coloring was measured using a color difference meter (manufactured by Tokyo Denshoku Co., Ltd., Model TCA-I) using 10 superimposed samples with the coated side facing up.
Expressed as YELLOW INDEX. Example 1 In a glass-lined autoclave with stirring blades 70 parts of deionized water Alkyl diphenyl ether Sodium disulfonate 0.1 part (Newcol 271A manufactured by Nippon Nyukazai Co., Ltd.) Polyoxyethylene nonyl phenol ether 0.2 parts (manufactured by Kao Atlas Co., Ltd.) Emulgen 935) Potassium persulfate 0.01 part Sodium hydrogen sulfite 0.01 part were charged all at once, and the mixture was sufficiently replaced with nitrogen gas. Then, 9.2 parts vinylidene chloride, 0.2 parts acrylonitrile, and 0.6 parts methyl methacrylate were rapidly added using a pump, and the mixture was heated at 45°C for 3 hours. After stirring (seed polymerization), 6.0 parts of a 1% aqueous solution of sodium bisulfite was added, and then a mixture of 69 parts of vinylidene chloride, 1.5 parts of acrylonitrile, and 4.5 parts of methyl methacrylate was continuously added at a rate of 5 parts per hour. . At the same time, a mixture of 0.3 parts of alkyl diphenyl ether sodium disulfonate, 0.8 parts of polyoxyethylene nonyl phenol ether, 0.004 parts of potassium persulfate, and 17.0 parts of deionized water was continuously added at a rate of 1 part per hour. Immediately after completing the addition of the entire monomer mixture, add 2 parts of 1% sodium bisulfite aqueous solution to prepare the following monomer mixture: Vinylidene chloride 13.5 parts Acrylonitrile 0.6 parts Methyl acrylate 0.6 parts Acrylic acid 0.3 parts This mixture was continuously added at a rate of 5 parts per hour. After the monomer addition was completed, the emulsifier and polymerization initiator additions were also completed. After 1 hour, a mixture of 0.02 parts of potassium persulfate, 0.02 parts of sodium bisulfite, and 4.0 parts of deionized water was added, stirred at 45°C for 3 hours, and the latex was tested according to the evaluation test method described above. Example 2 Polymerization was carried out by changing the monomer composition, emulsifier composition, and amount of initiator in Example 1 and the initial batch charging as follows. Composition of the initial bulk charging emulsifier Dodecylbenzenesulfonic acid Polyoxyethylene sorbitan Fatty acid ester 0.3 parts Initiator amount Potassium persulfate 0.015 parts Sodium bisulfite 0.015 parts Monomer composition Vinylidene chloride 9.1 parts Methyl methacrylate 0.5 parts Methacrylonitrile 0.4 parts Further, the composition of the emulsifier to be continuously added, the amount of initiator, and the composition of the monomer to be continuously added at the beginning were as follows. Sodium dodecylbenzenesulfonate 0.3 parts Polyoxyethylene sorbitan Fatty acid ester 1.2 parts Potassium persulfate 0.008 parts Vinylidene chloride 68.25 parts Methyl methacrylate 3.75 parts Methacrylonitrile 3.0 parts Monomer composition to be continuously added Vinylidene chloride 13.5 parts Methyl acrylate 0.6 parts Acrylonitrile 0.6 parts Acrylic acid 0.3 parts The amounts of initiators to be added 1 hour after the end of continuous addition of emulsifier and polymerization initiator are: Potassium persulfate 0.03 parts Sodium hydrogen sulfite 0.03 parts. Polymerization was carried out in the same manner as in Example 1 except for the above points to obtain a latex. Example 3 50 parts of deionized water and 0.01 part of sodium bisulfite were charged into a glass-lined autoclave equipped with a stirring blade, and the mixture was thoroughly purged with nitrogen, heated to 45°C, and 0.1 part of sodium alkyl diphenyl ether disulfonate polyoxyethylene nonyl phenol ether A mixture of 0.5 part (Emulgen 930 manufactured by Kao Atlas Co., Ltd.), 0.01 part of potassium persulfate, and 15 parts of deionized water was continuously added in its entirety in one hour. 10 minutes after starting the addition of the above mixture of emulsifier and polymerization initiator, a mixture of 90 parts of vinylidene chloride, 7 parts of methyl acrylate, and 3 parts of glycidyl methacrylate was continuously added at a rate of 5 parts per hour. It started. After adding 7 parts of a 1% aqueous solution of sodium bisulfite 50 minutes after starting the monomer addition Sodium alkyl diphenyl ether disulfonate 0.2 parts Polyoxyethylene nonyl phenol ether 1.0 parts Potassium persulfate 0.004 parts Deionized A mixture of 19.5 parts of water was added at a rate of 1 part per hour. One hour after the addition of the entire monomer mixture was completed, a mixture of 0.02 parts of potassium persulfate, 0.02 parts of sodium bisulfite, and 4.0 parts of deionized water was added, and the mixture was further stirred at 45°C for 3 hours to obtain a latex. Comparative Example 1 A latex was obtained by carrying out polymerization in the same manner as in Example 1 except for the following points. 1 In the initial bulk charge, 0.1 part of sodium alkyl diphenyl ether disulfonate, 0.2 part of polyoxyethylene nonylphenol ether
0.5 parts of sodium alkyl diphenyl ether disulfonate is added in place of 0.5 parts of sodium alkyl diphenyl ether disulfonate. 2. As the emulsifier, use only the above-mentioned anionic emulsifier that is charged all at once, and do not continuously add the emulsifier during the polymerization. The properties of the latex and copolymer obtained are shown in Table 1. Since the latex used only an anionic emulsifier, it naturally had poor chemical stability.
Moreover, the molecular weight of the obtained copolymer was 1/2 compared to that of Example 1, and the light coloring resistance was poor. Comparative Example 2 After polymerization, 2.5 parts of a nonionic emulsifier was added to the latex obtained in Comparative Example 1. The stability of the latex toward cationic emulsifiers is improved, but the stability toward methanol is not.
The properties of the copolymer were extremely poor in gas barrier properties and light coloring resistance. Comparative Example 3 After polymerization, 1.5 parts of a nonionic emulsifier was added to the latex obtained in Comparative Example 1. Since the amount of nonionic emulsifier was smaller than in Comparative Example 2, stability could not be maintained even with respect to cationic emulsifier. Comparative Example 4 Polymerization was carried out in the same manner as in Example 1, except that 2.5 parts of polyoxyethylene nonyl phenol ether was used instead of 0.8 parts of polyoxyethylene nonyl phenol ether in the continuous addition of the emulsifier and polymerization initiator in Example 1. I went there. At the same amount of initiator, the polymerization rate was slightly delayed. Since the amount of nonionic emulsifier used was larger than the range of the present invention, the chemical stability of the latex and the light coloring resistance of the copolymer were excellent, but only a product with poor gas barrier properties was obtained. Comparative Example 5 Polymerization was carried out in the same manner as in Example 1 except for the following points. The polymerization of the seed latex was the same, but after the completion of the seed polymerization, 0.1 part of sodium alkyl diphenyl ether disulfonate and 0.5 part of polyoxyethylene nonyl phenyl ether were added, and the same monomer composition and the same monomer composition as in Example 1 were added. A mixed aqueous solution of an emulsifier and an initiator was continuously added in the same manner as in Example 1. The amount of emulsifier added continuously was 55% of the total emulsifier. The obtained latex coagulated in methanol and partially coagulated in cationic emulsifier, and had poor chemical stability. Furthermore, the extraction rate of the emulsifier extracted with methanol due to its copolymerizability was 77%, which was quite high. Although the molecular weight of this copolymer was slightly higher, it was not at a level that could sufficiently improve the light resistance. Comparative Example 6 A seed latex was polymerized using the same monomer composition and the same method as in Example 1. To this latex were added 0.05 parts of potassium persulfate, 0.03 parts of sodium bisulfite, and 8.0 parts of deionized water as initiators. Next, a monomer mixture having the same composition and amount as in Example 1 was continuously added at a rate of 5 parts per hour, and at the same time 0.3 parts of sodium alkyl diphenyl ether disulfonate and 0.8 parts of polyoxyethylene nonyl phenol ether were added. A mixture of 17 parts of ionized water was added continuously at a rate of 1 part per hour. Next, after 10 hours of continuous addition of the monomer mixture and emulsifier mixture, 0.02 parts of potassium persulfate, 0.02 parts of sodium bisulfite, and 40 parts of deionized water were added all at once. After the first continuous addition of monomers was completed (15 hours), again 0.03 parts of potassium persulfate, 0.03 parts of sodium bisulfite, and 6.0 parts of deionized water were added, and the second monomer mixture was prepared as in Example 1. Similarly, it was added continuously. After the addition was completed, 0.02 parts of potassium persulfate, 0.02 parts of sodium bisulfite, and 4.0 parts of deionized water were added, and the mixture was further stirred at 45°C for 3 hours to obtain a latex. In Comparative Example 6, since the polymerization initiator was not continuously added, the chemical stability of the obtained latex was poor, and it was coagulated with methanol. In addition, some of the cationic emulsifiers coagulated. The molecular weight of the copolymer was quite small, partly because a large amount of initiator was used to complete the polymerization (reducing the amount of initiator resulted in an extremely low polymerization yield). Furthermore, the light coloring resistance was extremely poor, probably due to the high content of metal ions. Comparative Example 7 Polymerization was carried out in the same manner as in Example 3 except for the method of adding an initiator. The method and amount of addition of the initiator were the same as in Comparative Example 6. The stability of the latex was as poor as in Comparative Example 6. Compared to Example 3, the molecular weight was significantly lowered and the light coloring resistance was extremely poor. A comparison with Comparative Example 6 shows the difference in that although the amount of initiator was the same, a monomer having a stabilizing effect against heat and light was used in the monomer composition. The polymerization recipes and results of Examples 1 to 3 and Comparative Examples 1 to 7 are shown in Table 1.

【table】

[Table] From the above examples and comparative examples of the present invention, monomers,
In the latex obtained by emulsion copolymerization by simultaneously and continuously adding an emulsifier and an initiator, the nonionic emulsifier is tightly bound to the latex-like copolymer, and a very small amount can improve the stability of the latex. It is something that can be maintained. As a result, the gas barrier properties of the copolymer were improved because an extremely small amount of emulsifier was required, and the light coloring resistance was also improved by controlling the compositional distribution and molecular weight distribution of the copolymer using the copolymerization method of the present invention. Example 4 In a glass-lined autoclave with stirring blades 70 parts of deionized water Alkyl diphenyl ether Sodium disulfonate 0.15 parts (Newcol 271A manufactured by Nippon Nyukazai Co., Ltd.) Polyoxyethylene nonyl phenol ether 0.25 parts (manufactured by Kao Atlas Co., Ltd.) Emulgen 935) Charge 0.01 part of potassium persulfate and 0.01 part of sodium hydrogen sulfite, and after thoroughly purging with nitrogen gas, rapidly add 9.0 parts of vinylidene chloride, 0.7 parts of methyl methacrylate, 0.3 parts of acrylonitrile using a pump, and stir at 45°C for 3 hours. rear,
6.0 parts of a 1% aqueous solution of sodium bisulfite were added, and then a mixture of 81.9 parts vinylidene chloride, 2.7 parts methyl methacrylate, 2.7 parts acrylonitrile, and 2.7 parts glycidyl methacrylate was continuously added at a rate of 5 parts per hour. At the same time, sodium alkyl diphenyl disulfonate
A mixture of 0.5 parts polyoxyethylene nonyl phenol ether 0.75 parts potassium persulfate 0.008 parts deionized water 18 parts was added at a rate of 1 part per hour. Ten hours after starting the continuous addition, 3.0 parts of a 1% aqueous solution of sodium bisulfite was added. One hour after the addition of the entire monomer mixture was completed, a mixture of 0.02 parts of potassium persulfate, 0.02 parts of sodium bisulfite, and 4.0 parts of deionized water was added, and stirring was continued for an additional 3 hours at 45°C to obtain a latex. . The properties of this latex and the results of evaluating the physical properties of the copolymer are shown in Table 1. Example 5 In a glass-lined autoclave with stirring blades Deionized water 70 parts Sodium alkylsulfonate 0.20 parts (Melsolat H manufactured by Bayer) Polyoxyethylene nonyl phenol ether 0.30 parts (Emulgen 935 manufactured by Kao Atlas Co., Ltd.) Potassium persulfate 0.01 After charging 0.01 part of sodium bisulfite and thoroughly purging with nitrogen gas, the mixture was heated to 45°C, and a mixture of 9.0 parts of vinylidene chloride, 0.7 parts of methyl methacrylate, and 0.3 parts of glycidyl methacrylate was rapidly added using a pump, and after stirring for 3 hours, the mixture was stirred for 3 hours. 6.0 parts of a 1% aqueous sodium hydrogen solution was added, and then a mixture of 67.5 parts of vinylidene chloride, 3.0 parts of methyl methacrylate, 3.0 parts of methacrylonitrile, and 1.5 parts of glycidyl methacrylate was added at a rate of 5 parts per hour. At the same time, 0.6 parts of sodium alkyl sulfonate polyoxyethylene nonyl phenol ether
A mixture of 1.0 part potassium persulfate, 0.008 part deionized water, and 18.0 parts was added at a rate of 1 part per hour. Immediately after the addition of the monomer mixture was completed, 2.0 parts of a 1% aqueous solution of sodium bisulfite was added, followed by the addition of a mixture of 13.5 parts of vinylidene chloride, 0.6 parts of acrylonitrile, and 0.9 parts of methyl acrylate at a rate of 5 parts per hour. . After the monomer addition was completed, the addition of the emulsifier and polymerization initiator was also stopped. After 1 hour, a mixture of 0.02 parts of potassium persulfate, 0.02 parts of sodium bisulfite, and 4.0 parts of deionized water was added, and the mixture was stirred at 45°C for 3 hours to obtain a latex. Comparative Example 8 In Example 4, in the initial charge, 0.15 part of sodium alkyldiphenyldisulfonate and 0.25 part of polyoxyethylene nonylphenol ether were replaced with 0.4 part of sodium alkyldiphenyldisulfonate.
Polymerization was carried out in the same manner as in Example 4, except that 1.2 parts of sodium alkyldiphenylsulfonate was used in place of 0.5 parts of sodium alkyldiphenyldisulfonate and 0.75 parts of polyoxyethylene nonyl phenyl ether in the continuous addition. The obtained latex had poor chemical stability and was inferior in light coloring resistance compared to Example 4. Comparative Example 9 In Example 4, 0.7 parts of sodium alkyl diphenyldisulfonate and 0.9 parts of polyoxyethylene nonylphenol ether were used in the initial charging,
Polymerization was carried out in the same manner as in Example 4, except that no emulsifier was used in the continuous addition. The obtained latex had a high emulsifier extraction rate, poor chemical stability, and was inferior to Example 4 in light coloring resistance and gas barrier properties. The polymerization recipes and results of Examples 4 and 5 and Comparative Examples 8 to 9 are collectively shown in Table 2.

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【table】

Claims (1)

[Scope of Claims] 1. 100 parts by weight of a monomer mixture consisting of 60 to 94% by weight of vinylidene chloride and 6 to 40% by weight of a monomer copolymerizable with vinylidene chloride, and 0.03 parts by weight of an anionic emulsifier.
-1.0 parts by weight and 0.1 to 1.5 parts by weight of a nonionic emulsifier, in which the monomer mixture is subjected to emulsion polymerization in the presence of a polymerization initiator and an emulsifier mixture in which the nonionic emulsifier accounts for 60% by weight or more of the total emulsifier.
Up to 20% by weight of 100 parts by weight of the emulsifier mixture
After carrying out emulsion polymerization in advance using not more than 30% by weight of the monomer mixture and not more than 30% by weight of the polymerization initiator, continuously and uniformly adding 80% by weight or more of the monomer mixture,
The extraction rate of the emulsifier from the copolymer with methanol is used, characterized in that 75% by weight or more of the emulsifier mixture and all or a part of the remaining polymerization initiator are continuously and uniformly added during the continuous addition period. A method for producing a vinylidene chloride copolymer latex containing 50% by weight or less of an emulsifier. 2 The monomer mixture is 60 to 94% by weight of vinylidene chloride, 0.5 to 10% by weight of methacrylonitrile or acrylonitrile, and 0.5% of glycidyl methacrylate.
~5% by weight and 0 monomers copolymerizable with these
25% by weight of a vinylidene chloride copolymer latex according to claim 1.