JPH0616736A - Production of copolymer latex - Google Patents

Abstract

PURPOSE:To obtain a copolymer latex by a new method, providing coated paper having excellent backing roll stain resistance and bond strength as a binder for coating paper and also suitable as a binder for carpet back sizing. CONSTITUTION:In subjecting a monomer mixture comprising (A) an aliphatic conjugated diene-based monomer (preferably butadiene), (B) an ethylenic unsaturated carboxylic acid monomer and a monomer (preferably styrene, methyl methacrylate, etc.) copolymerizable with these monomers to emulsion polymerization in the presence of a cyclic unsaturated hydrocarbon containing an unsaturated bond in the ring (preferably cyclopentene), first the monomer mixture containing the component A is added and polymerized. Successively, after the addition of the monomer mixture containing the component A is completed, a monomer mixture not containing the component A is added and polymerized. The amount of the monomer mixture not containing the component A added at the second half of the polymerization is preferably 3-40wt.% based on the total amounts of the monomers used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel method for producing a copolymer latex. More specifically, it relates to a method for producing a copolymer latex which is preferably used as a binder in the field of paper processing or backsizing of carpets.

[0002]

2. Description of the Related Art It is well known that a so-called butadiene copolymer latex containing butadiene as a main component is widely used as a binder in the field of paper processing or back sizing of carpets.

For example, for the purpose of improving printability of paper and improving optical properties such as gloss and opacity, a pigment such as kaolin and calcium carbonate and a copolymer latex or starch as a binder are formed on the surface of a raw paper which has been made. A paint mainly composed of a water-soluble polymer such as casein is applied. This copolymer latex is a synthetic product unlike the water-soluble polymer that is the other binder, so that it is easy to modify and satisfy the performance required for the above coated paper.
Its composition and structure are changed.

By the way, in recent years, in the printing process using coated paper, speeding up of printing has been promoted in order to improve the productivity, and accordingly, the adhesive strength of the binder called dry pick is insufficient. It is becoming more likely that printing defects will occur due to this, and there is a strong demand for improvements in the copolymer latex. Generally, in order to increase the adhesive strength, the proportion of the aliphatic conjugated diene (butadiene), which is one component in the copolymer latex, is increased. This is to increase the adhesive strength by increasing the tackiness of the copolymer latex, but this method causes one of the following operational problems during the production of coated paper. .

Generally, most of the papers used for printing papers are coated papers coated on both sides. In such double-sided coating, first of all, the first coater is applied on one side, and after drying,
In the process of coating the back surface with the second coater, the coating layer on the front surface adheres to and accumulates on the roll supporting the paper, and the roll becomes dirty, so-called backing roll dirt occurs. When such roll stains occur, not only the coated paper properties such as smoothness and gloss are deteriorated, but also coating may have to be interrupted in order to clean the roll stains. Will be invited.

[0006] Such backing roll stains are also considered to be due to the tackiness of the copolymer latex used as a binder. Thus, in order to improve the adhesive strength of the coated paper, it is necessary to simply use the copolymer weight. Increasing the proportion of the aliphatic conjugated diene in the coalesced latex results in promoting backing roll fouling. For this reason,
Although improvement of the above-mentioned copolymer latex has been studied so far to solve this problem, none of these conventional copolymer latexes was sufficiently satisfactory. Therefore, there is a strong demand for a copolymer latex capable of providing a coated paper having an excellent balance between the adhesive strength and the backing roll stain resistance that can cope with the recent increase in printing speed.

Further, these copolymer latexes are
Adhesives for carpet backing such as tufted carpets and needle punched carpets, cushioning materials for automobiles,
It is also used as an adhesive for rock fiber bases used in applications such as civil engineering mats and industrial filters, and also in these applications, a copolymer latex having sufficient adhesive strength is required.

[0008]

As described above, in the conventional copolymer latex, the adhesive strength and the backing roll stain resistance which are required with the recent increase in printing speed cannot be said to be sufficient. It cannot be said that the adhesive strength required for other uses is sufficient.

[0009]

[Means for Solving the Problems] As a result of intensive studies on the above problems, the present inventors have found that when an emulsion polymerization of a monomer in the presence of a specific compound is performed, an aliphatic conjugated diene-based monomer is used. The present invention has been achieved by finding that the above problems can be solved by adding a monomer mixture containing no component (a) after the addition of the monomer mixture containing the body (a) is completed. Is.

That is, the present invention has one unsaturated bond in the ring.
Aliphatic conjugated diene monomer (a), ethylenically unsaturated carboxylic acid monomer (b), and other monomers copolymerizable with these in the presence of a cyclic unsaturated hydrocarbon having two ( In the emulsion polymerization of (c), after the addition of the monomer mixture containing the above-mentioned component (a), a monomer mixture containing no (a) component is further added to produce a copolymer latex. It provides a method.

The present invention will be described in detail below.

Examples of the aliphatic conjugated diene-based monomer (a) in the present invention include 1,3-butadiene and 2-methyl-
1,3-Butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like, one kind or Two or more types can be used. Particularly, 1,3-butadiene is preferable.

Ethylenically unsaturated carboxylic acid monomer (b)
Examples thereof include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid.

The other monomer (c) copolymerizable with the aliphatic conjugated diene monomer (a) and the ethylenically unsaturated carboxylic acid monomer (b) is an alkenyl aromatic monomer. , Unsaturated carboxylic acid alkyl ester monomers, hydroxyalkyl group-containing unsaturated monomers, vinyl cyanide monomers, unsaturated carboxylic acid amide monomers, and the like.

As the alkenyl aromatic monomer, styrene, α-methylstyrene, methyl α-methylstyrene,
Vinyltoluene and divinylbenzene and the like,
One kind or two or more kinds can be used. Particularly preferred is styrene.

The 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 malate, dimethyl. Itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like can be mentioned, and one kind or two or more kinds can be used. Methyl methacrylate is particularly preferable.

Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate and β-hydroxyethyl acrylate.
-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-hydroxyethylmethyl fumarate, etc. are mentioned, and 1 type (s) or 2 or more types can be used. Particularly, β-hydroxyethyl acrylate is preferable.

Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and α-ethylacrylonitrile.
One kind or two or more kinds can be used. Acrylonitrile is particularly preferable.

As the unsaturated carboxylic acid amide monomer,
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
N-dimethylacrylamide and the like can be mentioned, and one kind or two or more kinds can be used. Particularly preferred is acrylamide.

Further, in addition to the above monomers, fatty acid vinyl esters such as vinyl acetate and vinyl propionate,
It is possible to use basic monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-vinylpyridine and 4-vinylpyridine, vinyl chloride, vinylidene chloride and the like. it can.

The above monomer composition is not particularly limited,
Aliphatic conjugated diene-based monomer (a) 10 to 80% by weight, ethylenically unsaturated carboxylic acid monomer (b) 0.5 to 10% by weight, and other monomer (c) 10 copolymerizable therewith ~
It is preferably 89.5% by weight.

If the amount of the aliphatic conjugated diene monomer (a) is less than 10% by weight, the adhesiveness tends to be poor, and if it exceeds 80% by weight, the water resistance tends to be poor. If the ethylenically unsaturated carboxylic acid monomer (b) is less than 0.5% by weight, mechanical stability is poor, and if it exceeds 10% by weight, the viscosity of the latex tends to increase, which is not preferable. If the other copolymerizable monomer (c) is less than 10% by weight, the water resistance is 89.5%.
If it exceeds 5% by weight, the adhesion tends to be poor, which is not preferable.

In the present invention, among the above-mentioned monomers, first, after the addition of the monomer mixture containing the aliphatic conjugated diene monomer (a) component, the monomer containing no (a) component is further added. Add the mixture. If this condition is not satisfied, that is, if the aliphatic conjugated diene monomer (a) is added in the latter half of the polymerization, the improvement in the balance between the adhesive strength and the backing roll stain resistance, which is the object of the present invention, cannot be expected. The amount of the monomer mixture containing no component (a) added in the latter half is preferably in the range of 3 to 40% by weight based on the total amount (total) of the monomers used. If it deviates, the effect of improving the physical property balance becomes small.

The chain transfer agent used in the present invention includes
Alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, xanthogen compounds such as dimethylxanthogen disulfide, diisopropylxanthogen disulfide, α- Methylstyrene dimer, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide,
Thiuram-based compounds such as tetramethylthiuram monosulfide, 2,6-di-t-butyl-4-methylphenol, phenol-based compounds such as styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane, dibromomethane and carbon tetrachloride. , Halogenated hydrocarbon compounds such as carbon tetrabromide, α-benzyloxystyrene, α-benzyloxyacrylonitrile, vinyl ethers such as α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid , Thiomalic acid, 2-ethylhexyl thioglycolate and the like, and one or more of them can be used.

The amount of the chain transfer agent used is not particularly limited and can be appropriately adjusted according to the performance required for the copolymer latex, but preferably 0.05 to 100 parts by weight of the monomer mixture. 10 parts by weight.

The cyclic unsaturated hydrocarbon having one unsaturated bond in the ring used in the present invention has a boiling point of 140 ° C. or lower because it is necessary to recover unreacted substances after the polymerization is completed. preferable. Specific examples include cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and the like.

The amount of the above compound used in the present invention is 0.1 to 30 parts by weight based on 100 parts by weight of the monomer mixture. If the amount is less than 0.1 parts by weight, the effect of the present invention is insufficiently expressed, and if the amount exceeds 30 parts by weight, the amount of the compound remaining as an unreacted product relatively increases, and the energy required for recovery increases. Not preferable. Preferably 0.5
~ 15 parts by weight.

The method of adding various components in the present invention is not particularly limited, and any of a batch addition method, a divided addition method and a continuous addition method can be adopted. Further, in the emulsion polymerization, a commonly used emulsifier, polymerization initiator, electrolyte, polymerization accelerator, chelating agent and the like can be used.

In the present invention, any of two-step polymerization, multi-step polymerization, power feed polymerization and the like can be adopted, but emulsion polymerization is particularly preferable by the following method.

That is, in the first step, a mono-monomer containing 3 to 40% by weight of the aliphatic conjugated diene monomer (a) and the ethylenically unsaturated carboxylic acid monomer (b) with respect to all the monomers. Polymerization was carried out by adding the body mixture, and then 2
After adding the monomer mixture containing 0 to 94% by weight of the aliphatic conjugated diene monomer (a), the third step is further performed in 3 to 4 steps.
Polymerization is continued by adding 0% by weight of a monomer mixture containing no component (A), and the polymerization is substantially completed.

As the emulsifier, anionic surfactant such as sulfuric acid ester salt of higher alcohol, alkylbenzene sulfonate, aliphatic sulfonate, aliphatic carboxylate, sulfuric acid ester salt of nonionic surfactant, or polyethylene glycol. One or more nonionic surfactants such as alkyl ester type, alkyl phenyl ether type, and alkyl ether type are used.

As the initiator, a water-soluble initiator such as potassium persulfate, ammonium persulfate or sodium persulfate, a redox type initiator, or an oil-soluble initiator such as benzoyl peroxide can be used.

By adopting the above-mentioned production method, it is possible to obtain a copolymer latex which provides a coated paper having an excellent balance of adhesive strength and backing roll stain resistance. The cyclic unsaturated hydrocarbon having one unsaturated bond in the ring is not preferable in terms of the working environment hygiene in the end use, so in the present invention, after polymerizing the copolymer latex by the production method, The compound remaining as an unreacted substance was substantially (based on 100 parts by weight of the copolymerized latex (solid content)).
0.5 parts by weight or less, more preferably 0.1 parts by weight or less).

As a method for removing the compound, a known method,
For example, it can be removed by steam distillation, vacuum distillation, blowing of an inert gas, or the like.

The copolymer latex obtained by the above-described production method can be used as a binder for pigments, other binders, and auxiliary agents for paper coating, and is obtained by applying the coating. The coated paper obtained has an excellent balance between adhesive strength and backing roll stain resistance. Further, the copolymer latex can be used as a binder not only for paper coating but also for carpet backing, rock fiber base material, tire cord, wood, leather and the like.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples, parts and percentages are based on weight. The physical properties in the examples were measured by the following methods.

A latex film is prepared by drying the gel content at room temperature. After accurately weighing about 1.0 g of latex film, put it in 400 cc of toluene, leave it for 48 hours to dissolve it, filter through a 300-mesh wire net, dry it, measure the toluene insoluble content (gel) on the wire net, and calculate the gel content. To do.

The degree of picking when printed with a RI Dry Pick RI printing machine without using dampening water was judged with the naked eye, and grade 1 to grade 5 (best)
It was evaluated by a five-level method of the grade (the worst one). The average value of 6 times is shown.

A backing roll stain resistant coated paper sample (unprocessed super calendar) was overlaid on a polyester film so that the coated surface was in contact, and then hot pressed with a 200 kg hot roll heated to 120 to 130 ° C. To do. The stains adhered on the polyester film are visually evaluated to evaluate the stain resistance of the backing roll. 1.0 (Small dirt is good) to 5.0 (Small dirt is bad)

Preparation of copolymer latex In a 10 liter autoclave, 100 parts by weight of water, 0.4 part of sodium dodecylbenzenesulfonate, 0.3 part of sodium hydrogencarbonate, 1.0 part of potassium persulfate and Table 1 or Table. The first-stage monomer mixture shown in 2, a chain transfer agent, and a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring were charged, and the first-stage polymerization was carried out at 65 ° C. When the conversion rate of the first-stage emulsion polymerization reached 70%, the second-stage monomer mixture and the chain transfer agent were continuously added for 6 hours to carry out the second-stage polymerization. After that, the monomer mixture of the third stage and the chain transfer agent were continuously added for 1 hour to carry out the polymerization of the third stage. In order to complete the polymerization, the reaction was further continued, and the polymerization was completed when the conversion of polymerization was 98%. The obtained copolymer latex was adjusted to pH 8 with sodium hydroxide, and then unreacted monomers and unsaturated hydrocarbons remaining as unreacted products were removed by steam distillation to obtain a copolymer latex 1 And 4 were obtained.

Regarding the copolymer latexes 2, 3, 5, and 6, the polymerization conversion ratio was 98 after continuously adding the second-stage monomer and the like for 7 hours without adding the third-stage monomer and the like. The reaction was continued until the amount reached%, and the polymerization was completed. Hereinafter, in the same manner as the copolymer latex 1, the copolymer latexes 2, 3,
5 and 6 were obtained.

The copolymer latex 7 was polymerized in the same manner as the copolymer latex 4 except that cyclohexane was changed to cyclohexane. Thereafter, copolymer latex 7 was obtained in the same manner as copolymer latex 4.

In the table, the amount after "//" is inserted is the first stage on the left side, the second stage is on the center, and the third stage is the amount on the right side after addition of the monomers.

Preparation of paint for paper coating (I) Copolymer latices 1 to 3 were used to prepare a solid content concentration of 62% based on the following formulation, and pure water was used to prepare the mixture for paper coating. Got the paint.

(Formulation I) Kaolin clay 80 parts Heavy calcium carbonate 20 parts Modified starch 5 parts Copolymer latex 12 parts (solid content) ─────────────────── ────── Solid content 62%

Commercially available high-quality paper (64 g / m ² ) was coated and dried using a coating bar so that the coating amount of the above composition was 13 g / m ^{2 on} one side, and a coated paper was obtained. The backing roll stain resistance of the obtained coated paper was evaluated. Further, the obtained coated paper was subjected to a super calendar treatment under the conditions of a roll temperature of 50 ° C. and a linear pressure of 70 to 80 kg / cm, and then RI Dry Pick was measured.

Preparation of paint for paper coating (II) Copolymer latices 4 to 7 were used to prepare a solid content concentration of 62% based on the following formulation, respectively, using pure water to prepare a paper coating. Got the paint.

(Formulation II) Kaolin clay 60 parts Heavy calcium carbonate 40 parts Modified starch 6 parts Copolymer latex 10 parts (solid content) ─────────────────── ────── Solid content 62%

A commercial high-quality paper (64 g / m ² ) was coated and dried using a coating bar so that the coating amount of the above composition would be 10 g / m ^{2 on} one side, to obtain a coated paper. The backing roll stain resistance of the obtained coated paper was evaluated. Further, the obtained coated paper was subjected to a super calendar treatment under the conditions of a roll temperature of 50 ° C. and a linear pressure of 70 to 80 kg / cm, and then RI Dry Pick was measured.

The results are shown in Table 3.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

[0054]

By using the copolymer latex obtained in the present invention as a binder for paper coating, a coated paper excellent in backing roll stain resistance and adhesive strength can be obtained. In addition, the final product having excellent adhesive strength can be obtained in other applications such as carpet backsizing.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C08L 9/10 LAZ 8218-4J D06M 15/693 D21H 19/56

Claims (1)

[Claims] 1. An aliphatic conjugated diene monomer (a) and an ethylenically unsaturated carboxylic acid monomer (b) in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring. In addition, when emulsion-polymerizing another monomer (c) copolymerizable therewith, after the addition of the monomer mixture containing the component (a), a monomer mixture not containing the component (a) is added. A method for producing a copolymer latex, which comprises adding.