JPH07216018A - Method for deodorizing copolymer latex - Google Patents

Abstract

PURPOSE:To deodorize a copolymer latex for binder, etc., of a paper coating composition for web offset printing coated paper by treating a copolymer latex obtained by using a compound containing a mercapto group with an oxidizing agent. CONSTITUTION:1,3-Butadiene, styrene, methyl methacrylate, fumaric acid, potassium persulfate, water, a sodium alkylbenzenesulfonate and 2-mercaptoethyl octanate are charged into an autoclave substituted with nitrogen and reaction of these monomers is carried out at 70 deg.C for 2hr under stirring, and then, 1,3-butadiene, styrene, methyl methacrylate, acrylic acid, methacrylic acid and 2- mercaptoethyl octanate which are the rest.s of monomers are added to the reactional system and reaction of these monomers is carried out at 70 deg.C for 15hr and an oxidizing agent such as hydrogen peroxide is added to the resultant copolymer latex and the reactional system is allowed to stand at 70 deg.C for 8hr and pH is adjusted to 7.5 to efficiently deodorize the objective copolymer latex which becomes a problem due to the odor of mercaptan.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for deodorizing a copolymer latex obtained by using a compound containing a mercapto group.

[0002]

2. Description of the Related Art Mercaptan emits a peculiar odor even if it is present in an extremely small amount, and has a problem in handling. However, in recent years, due to environmental problems, when synthesizing a copolymer latex, carbon tetrachloride, which has been conventionally used as a polymerization chain transfer agent, is becoming unusable, and mercaptan, which has the disadvantage of having a strong odor, should be used. There is no choice but to avoid it. Especially, among coated papers, the copolymer latex used for offset printing is required to have a low gel content of 30 to 65% by weight since the blister resistance is important, and a large amount of mercaptan is contained. It is necessary to use the above polymerization chain transfer agent. Therefore, unreacted mercaptan is present in the synthesized copolymer latex, which causes a problem of causing odor. Conventionally, as a method for removing mercaptan, washing with sulfuric acid, washing with alkali, and washing with water are generally used, but these methods are contained in hydrocarbons, aromatic compounds, etc. and a liquid inert to sulfuric acid or alkali. It is a method of removing mercaptan, and it is deteriorated by sulfuric acid and alkali. Further, JP-A-3-38531 discloses a method of removing mercaptan using a lead compound or a copper compound, but when this method is applied to a copolymer latex, odor is improved, This causes a problem that a color peculiar to metal ions is added to the copolymer latex. Therefore, it has been desired to develop a method for easily and effectively removing the mercaptan in the copolymer latex without changing the properties of the copolymer latex and removing the odor of the copolymer latex.

[0003]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies in view of the above-mentioned problems of the prior art, and as a result, a copolymer latex obtained by using a compound containing a mercapto group. Is treated with an oxidant,
It was found that the odor of the copolymer latex was remarkably improved, and as a result of further studies, the present invention was completed.

[0004]

The present invention provides a method for deodorizing a copolymer latex, which comprises treating the copolymer latex obtained by using a compound containing a mercapto group with an oxidizing agent. The present invention relates to a treated copolymer latex composition and a paper coating composition containing the latex composition. The present invention will be described in detail below. Examples of the copolymer latex targeted by the present invention include a copolymer latex synthesized by using a compound having a mercapto group as a polymerization chain transfer agent.

The compound containing a mercapto group is
For example, alkyl monothiols such as octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, t-hexadecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan, for example, 2-mercaptopropion. Acid, 3-mercaptopropionic acid, mercaptocarboxylic acid such as mercaptoacetic acid or a salt thereof (for example, ammonium mercaptoacetate), for example, mercaptodicarboxylic acid such as mercaptosuccinic acid or a salt thereof (for example,
Mercaptodicarboxylates), for example, 2-mercaptoethanol, 3-mercapto-1,2-propanediol, and other mercaptans having a hydroxyl group in the molecule, for example, 2-mercaptoethylamine and other thiols having an amino group in the molecule. Kinds, for example, 2-ethylhexyl mercaptoacetate, 2-ethylhexyl mercaptopropionate, mercaptocarboxylic acid alkyl ester such as tridecyl mercaptopropionate, for example, methoxybutyl mercaptoacetate, mercaptocarboxylic acid alkoxyalkyl ester such as methoxybutyl mercaptopropionate, For example, a carboxylic acid mercaptoalkyl ester such as 2-mercaptoethyl octanoate, for example, 1,10
-Decanedithiol, 1,14-tetradecanedithiol, p-benzenedithiol, m-xylenedithiol, p-xylenedithiol, ethylene glycol dithioglycolate, butanediol dithioglycolate,
Dithiol compounds such as ethylene glycol dithiopropionate, butanediol dithiopropionate, triglycol dimercaptan, for example, 1,5,10-decanetrithiol, 1,3,5-benzenetrithiol, trimethylolpropane tristhio Glycolate,
Trithiol compounds such as trimethylolpropane tristhiopropionate, trimethylolpropane tristhiobutanate, trimethylolpropane tristhiopentanate, trimethylolpropane tristhiohexanate, for example, pentaerythritol tetrakisthioglycolate, pentaerythritol tetrakisthio. Tetrathiol compounds such as propionate, pentaerythritol tetrakisthiobutanate, pentaerythritol tetrakisthiopentanate, pentaerythritol tetrakisthiohexanate, for example, mercaptoacetic acid 2-mercaptoethyl ester, mercaptoacetic acid 6-mercaptohexyl ester, mercaptoacetic acid 8-mercaptooctyl ester, 6-mercaptohexyl mercaptopropionate Ester, mercaptopropionic acid 8
-Mercaptooctyl ester, mercaptocarboxylic acid mercaptoalkyl ester such as 2-mercaptooctanoic acid 2-mercaptoethyl ester, dimercaptotriethylene disulfide, dimercaptodiethyl sulfide, 2,5-dimercapto-1,3,4-thiadiazole, 2- Di-n-butylamino-4,6-dimercapto-S-triazine, 2,4,6-trimercapto-S-
Examples thereof include polythiol compounds such as triazine. These may be used alone or in combination of two or more. Of these, alkyl mercaptan, mercaptoacetic acid 2-ethylhexyl ester, methoxybutyl mercaptoacetate, methoxybutyl mercaptopropionate, and 2-mercaptoethyl octoate are particularly preferably used.

[0006] Examples of the monomer used in the synthesis of the copolymer latex of the present invention include an ethylenically unsaturated monomer and / or a conjugated diene monomer. Examples of the ethylenically unsaturated monomer include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene and p-methylstyrene, such as methyl acrylate, ethyl acrylate, butyl acrylate and 2-hydroxy acrylate. Alkyl ester compounds of acrylic acid or methacrylic acid such as ethyl, methyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, etc. Ethylenic compounds such as acrylamide, methacrylamide, N, N-dimethylacrylamide, N-methylolacrylamide, etc. Cyanation of acrylamide or methacrylamide compounds of saturated carboxylic acids, for example vinyl esters of carboxylic acids such as vinyl acetate, such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile Vinyl compounds such as methylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, dibutylaminoethyl (meth)
Ethylenically unsaturated amine compounds such as acrylate, dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, 2-vinylpyridine and 4-vinylpyridine, such as acrylic acid, methacrylic acid and crotonic acid. Mention may be made of saturated monocarboxylic acid compounds, for example ethylenically unsaturated dicarboxylic acid compounds such as maleic acid, fumaric acid and itaconic acid, or anhydrides thereof, for example half esters such as methyl maleate and methyl itaconic acid. These may be used alone or in combination of two or more. Of these, styrene as the aromatic vinyl compound, methyl methacrylate, ethyl acrylate, and butyl acrylate as the alkyl ester compound, and acrylonitrile as the vinyl cyanide compound,
The ethylenically unsaturated monocarboxylic acid compound is preferably acrylic acid or methacrylic acid, and the ethylenically unsaturated dicarboxylic acid compound is preferably fumaric acid or itaconic acid.
The amount of ethylenically unsaturated monomer used is about 20 to 90% by weight, preferably about 40 to 80% by weight, based on the total monomer mixture.

Examples of the conjugated diene-based monomer used when synthesizing the copolymer latex in the present invention include:
1,3-butadiene, isoprene, 2-chloro-1,3
-Butadiene, 2-methyl-1,3-butadiene and the like. These monomers may be used alone or in combination of two or more. Of these, especially 1,3-
Butadiene is preferred. The amount of the conjugated diene-based monomer used is about 10 to 80% by weight, preferably about 20 to 60% by weight, based on the total monomer mixture. The copolymer latex targeted by the present invention is a conventionally known emulsion polymerization method, that is, an emulsion is prepared by adding a monomer mixture, a polymerization initiator, an emulsifier, a polymerization chain transfer agent, etc. to an aqueous medium (eg, water). It is obtained by carrying out polymerization. The present invention, the polymerization initiator used in the emulsion polymerization is not particularly limited, for example, inorganic persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, for example cumene hydroperoxide, benzoyl peroxide. Organic peroxides such as isopropylbenzene peroxide, and azo initiators such as azoisobutyronitrile can be used. These can be used alone or in combination of two or more. Of these, persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate are preferably used from the viewpoint of polymerization stability. The polymerization initiator can also be used as a so-called redox polymerization initiator in combination with a reducing agent such as sodium bisulfite and ferrous sulfate. The amount of the polymerization initiator used is usually about 0.1 to 5 parts by weight, preferably about 0.2 to 2 parts by weight, based on 100 parts by weight of all the monomers.

The emulsifier used in the emulsion polymerization is not particularly limited, and examples thereof include anionic interfaces such as sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium dodecyl diphenyl ether disulfonate, and sodium succinate dialkyl ester sulfonate. Nonionic surfactants such as polyoxyethylene alkyl esters and polyoxyethylene alkylallyl ethers, and amphoteric surfactants include, for example, lauryl betaine, salts of stearyl betaine such as alkyl betaine type salts, and lauryl-β. -Alanine, lauryldi (aminoethyl) glycine, octyldi (aminoethyl) glycine salts, and other amino acid type ones. These may be used alone or in combination of two or more. Of these emulsifiers,
Particularly, sodium dodecylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate and the like are preferable. The amount of the emulsifier used is usually about 0.05 to 2.5 parts by weight, preferably about 0.1 to 1.5 parts by weight, per 100 parts by weight of the total monomer mixture. If necessary, a chelating agent such as sodium ethylenediaminetetraacetate, a dispersant such as sodium formaldehyde sulfoxylate, and an inorganic salt may be added.

As the oxidizing agent used in the present invention, a water-soluble inorganic oxidizing agent is preferable. The water-soluble inorganic oxidant referred to here has a solubility of 10% by weight in water at 20 ° C.
The above-mentioned inorganic oxidizers are, for example, peroxides such as hydrogen peroxide and sodium peroxide, perborates such as sodium perborate and potassium perborate, sodium hypochlorite, sodium chlorate, and peroxides. Examples thereof include sodium chlorate. These are used alone or in combination of two or more. Of these, hydrogen peroxide and sodium perborate are particularly preferably used. The amount of the oxidizing agent added is about 0.02 to 2.
It is 0% by weight, preferably about 0.1-0.8% by weight.
The oxidizing agent is added immediately after the reaction of the copolymer latex or after the post-treatment. The post-processing referred to here is
It refers to a series of operations such as pH adjustment, steam distillation and concentration performed after the completion of the reaction of the copolymer latex. The deodorant-added copolymer latex is then allowed to stand, preferably with stirring, for about 4 hours to 1 week. Treatment temperature is 0-80
C., preferably room temperature to 80.degree. Since the copolymer latex obtained by the method of the present invention has almost no odor peculiar to mercaptan, it can be used as a binder for a paper coating composition.
Further, it can be used as various kinds of adhesives such as carpet backing agents, paints, industrial and household adhesives, etc. Among them, it is advantageously used as a binder for paper coating compositions. To obtain a paper coating composition, for example, kaolin clay, talc, titanium oxide, calcium carbonate, aluminum hydroxide, inorganic pigments such as satin white, for example, casein, starch, natural binders such as protein,
For example, a synthetic latex such as polyvinyl alcohol or polyvinyl acetate emulsion is appropriately blended by a known method. In addition, dispersants, defoamers, leveling agents, preservatives,
Known components such as a waterproofing agent and a release agent can be added as necessary. The paper coating composition can be applied using a conventionally known method, for example, an air knife coater, a blade coater, a roll coater, an applicator, or the like.

[0010]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples below. In addition, "%" and "part" in the examples are all based on weight. Example 1 5 parts of 1,3-butadiene, 6 parts of styrene, 2 parts of methyl methacrylate were added to a nitrogen-substituted 5 liter autoclave.
Fumaric acid 2 parts, potassium persulfate 0.5 part, water 100 parts,
0.1 part of sodium alkylbenzenesulfonate and 0.2 part of 2-mercaptoethyl octanoate were charged and reacted at 70 ° C. with stirring. After 2 hours, 30 parts of 1,3-butadiene which is the remaining monomer and 45 of styrene
Parts, 8 parts of methyl methacrylate, 1 part of acrylic acid, 1 part of methacrylic acid, and 2.0 parts of 2-mercaptoethyl octanoate were charged together with 0.5 part of sodium alkylbenzenesulfonate. After 15 hours of reaction time, the reaction was terminated when the polymerization conversion rate reached 97% or more (per 100 parts of monomer), 0.3 part of hydrogen peroxide was added, and the mixture was allowed to stand at 70 ° C. for 8 hours while stirring. . After that, it was cooled to 30 ° C. and adjusted to pH 7.5 ± 0.2 with sodium hydroxide. Next, steam was blown to remove unreacted monomers, and the solid content of the latex was concentrated to 50% to obtain the desired latex. Next, the obtained copolymer latex was applied to A4 size filter paper using a # 4 bar coater. After left at room temperature for 1 hour, UV irradiation was performed to check the odor. The results are shown in [Table 1].

Examples 2 to 5 were obtained in the same manner as in Example 1 except that the monomer composition, the polymerization chain transfer agent composition, the deodorant composition and the deodorizing conditions shown in Table 1 were used. The odor of the copolymer latex was checked. The results are shown in [Table 1]. Example 6 10 parts of 1,3-butadiene, 20 parts of styrene and 2 parts of methyl methacrylate were placed in a nitrogen-substituted 5 liter autoclave.
Parts, acrylonitrile 5 parts, fumaric acid 3 parts, acrylic acid 1 part, potassium persulfate 0.5 part, water 100 parts, sodium alkylbenzene sulfonate 0.1 part and 2-mercaptoethyl octanoate 2.0 parts, It reacted at 70 degreeC, stirring. After 2 hours, 45 parts of 1,3-butadiene, 5 parts of styrene, 5 parts of methyl methacrylate, 2 parts of acrylonitrile, and 1 part of fumaric acid, which are the remaining monomers.
Parts, acrylic acid 1 part, and 2-mercaptoethyl octoate 0.5 parts were added to sodium alkylbenzene sulfonate 0.
I prepared it with 5 copies. After a reaction time of 15 hours, when the polymerization conversion rate reached 97% or more (per 100 parts of monomer), 30
Cool down to ℃, pH 7.5 ± using sodium hydroxide
Adjusted to 0.2. Next, steam was blown in to remove unreacted monomers, and after concentration, 0.3 part of hydrogen peroxide was added, and the mixture was allowed to stand for 1 week at room temperature with stirring. Then, the solid content of the latex was adjusted to 50% to obtain the desired latex. The odor check method is the same as that in the first embodiment. The results are shown in [Table 1].

Examples 7 to 10 were obtained in the same manner as in Example 6 except that the monomer composition, the polymerization chain transfer agent composition, the deodorant composition and the deodorizing conditions shown in Table 1 were used. The odor of the copolymer latex was checked. The results are shown in [Table 1]. Comparative Examples 1 to 5, except that the deodorizing operation was not performed after the polymerization was performed with the monomer composition and the polymerization chain transfer agent composition described in [Table 2].
The odor of the obtained copolymer latex was checked in the same manner as in Example 1. The results are shown in [Table 2]. Comparative Examples 6 to 10 Copolymers obtained in the same manner as in Example 6 except that the deodorizing operation was not performed after the polymerization was performed using the monomer composition and the polymerization chain transfer agent composition described in [Table 2]. The odor of the combined latex was checked. The results are shown in [Table 2]. The odors in [Table 3] were irradiated with UV and checked for odor by the following method. UV irradiation device Nippon Batteries Co., Ltd. Focusing type GS UV irradiation condition Meta-Hara lamp MB-250N 2
Irradiation with a kW × 2 lamp for 1 second from a place having a height of 95 mm. After UV irradiation under the above conditions, the odor was checked by a sensory test. The larger the number in the five-level evaluation, the better the odor is. As is clear from the comparison of the examples shown in [Table 1] and the comparative examples shown in [Table 2] with each other, the copolymer latex is treated with an oxidant by comparing the experimental examples with the same conditions other than the deodorizing conditions. As a result, it can be seen that the odor is significantly reduced.

[0013]

EFFECT OF THE INVENTION The copolymer latex deodorized by the method of the present invention is a paper coating composition for coated paper, which is a problem due to odor caused by mercaptan, particularly for offset rotary printing. In addition to being advantageously used as a binder, it can also be advantageously used for various adhesive applications such as carpet backing agents, paints, and industrial and household adhesives.

[0014]

[Table 1]

[0015]

[Table 2]

Claims (10)

[Claims] 1. A method for deodorizing a copolymer latex, which comprises treating the copolymer latex obtained by using a compound having a mercapto group with an oxidizing agent. 2. The deodorizing method according to claim 1, wherein the oxidizing agent is an inorganic oxidizing agent. 3. The deodorizing method according to claim 1, wherein the oxidizing agent is a water-soluble oxidizing agent. 4. The deodorizing method according to claim 2, wherein the inorganic oxidizing agent is a peroxide. 5. The deodorizing method according to claim 2, wherein the inorganic oxidizing agent is a perborate. 6. The deodorizing method according to claim 4, wherein the peroxide is hydrogen peroxide. 7. The deodorizing method according to claim 5, wherein the perborate is sodium perborate. 8. The deodorizing method according to claim 1, wherein the copolymer latex is obtained by using a monomer mixture containing an ethylenically unsaturated monomer and / or a conjugated diene monomer. 9. A copolymer latex composition obtained by treating a copolymer latex obtained by using a compound having a mercapto group with an oxidizing agent. 10. A composition for paper coating comprising a copolymer latex composition obtained by treating a copolymer latex obtained by using a compound having a mercapto group with an oxidizing agent.