JPH04159340A - Production of new copolymer latex - Google Patents

Abstract

PURPOSE:To improve the pick strength of printed and coated paper, the adhesion of a carpet, and the adhesive strength of a self-adhesive by copolymerizing a conjugated diene, an ethylenically unsatd. carboxylic acid, and a monomer copolymerizable with those two monomers in the presence of a specific chain transfer agent component in emulsion. CONSTITUTION:A substed. alpha-methylstyrene dimer of the formula (wherein Ph is a benzene ring; and X and Y are each H, halogen, 1-4C alkyl, methoxy, hydroxyl, glycidyl, acetyl, or alkylmercapto) is compounded with a chain transfer agent contg. sulfur (e.g. octyl thioglycolate) in a wt. ratio of the former to the latter of 2-50, giving a chain transfer agent component. 100 pts.wt. monomer mixture comprising 20-90wt.% conjugated diene, 0.5-10wt.% ethylenically unsatd. carboxylic acid, and a monomer copolymerizable with those two monomers (e.g. styrene) is copolymerized in the presence of 0.05-10.0 pts.wt. the chain transfer agent component in emulsion.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a novel copolymer latex for use in paper coating, carpet backing, fiber bonding, or adhesives. [00021

[Prior Art] Conventionally, synthetic copolymer latex has been widely used, for example, as a binder for paper coating, a binder for carpet back sizing, a binder for binding fibers such as nonwoven fabrics and artificial leather, and an adhesive for various materials. . When a copolymer latex is used for such purposes, the copolymer latex is required to have strong adhesion. [0003] For example, coated paper contains kaolin clay, calcium carbonate, satin white, talc, titanium oxide, etc. on the surface of the base paper after papermaking, with the aim of improving the paper's printability and optical properties such as gloss. pigments, a copolymer latex as a binder, and a water-soluble polymer such as starch, polyvinyl alcohol, or carboxymethyl cellulose as a water-retaining agent or auxiliary binder. Conventionally, styrene-butadiene copolymer latex, so-called SB latex, which is obtained by emulsion polymerization of styrene and butadiene as main monomer components, has been widely used. [0004]In recent years, the production of coated paper has increased significantly as demand for color-printed magazines, pamphlets, and advertisements has increased. In particular, with the trend toward higher speed printing in offset printing, the quality requirements for coated paper and pigment binders are becoming increasingly sophisticated. Improvement is strongly required. Moreover, this pick strength performance has a negative correlation with other print properties, such as wet pick strength, blister resistance, halftone dot reproducibility, etc., so improvements that balance these physical properties to a high level are required. requested. [0005] Since these properties of coated paper are particularly strongly dependent on the design of the SB latex used as a pigment binder, various studies have been made on the performance of the SB latex. For example, it has been confirmed that the proportion of the insoluble portion of a copolymer latex film in solvents such as benzene, toluene, and tetrahydrofuran is the controlling factor for pick strength and blister resistance, so various studies have been conducted from this aspect. Specifically, it has been proposed to achieve excellent performance by adjusting the composition and gel fraction of the copolymer in latex within a specific range (Japanese Patent Publication No. 59-3598). , Japanese Patent Publication No. 60-17879, Japanese Patent Application Publication No. 58-4894). The gel fraction of this latex varies depending on various polymerization factors such as monomer composition and polymerization temperature, but a common and simple method for adjusting it to a desired level is to add a chain transfer agent. Conventionally, halogenated hydrocarbons such as carbon tetrachloride, alkyl mercaptans such as n- or n-dodecyl mercaptan, sulfides, and the like have been used as chain transfer agents. [0006] However, in general, the pick strength of coated paper is highest when the gel fraction is 75 to 95 percent in SB latex, whereas the blister resistance is determined by the weight of the gel fraction. It is accepted that the lower the value, the better it is.
None of the above techniques is fully satisfactory in order to simultaneously improve both pick strength and blister resistance to a high level. [0007] Furthermore, the fraction of butadiene units that is optimal for wet pick strength in offset printing is 34% by weight or less, which is different from the fraction of butadiene units that is optimal for pick strength.
It was difficult to achieve high levels of both physical properties at the same time. In addition, good halftone dot reproducibility and super calendar stain resistance during coated paper production are particularly important for gravure printing paper. However, since this product is designed to have a high butadiene unit fraction, the halftone dot reproducibility can be sufficiently improved without impairing supercalendar stain resistance. Not yet reached. [0008] Additionally, carpet back sizing adhesives are generally compositions in which copolymer latex is blended with fillers such as calcium carbonate or aluminum hydroxide, and other additives such as thickeners. This adhesive composition is used in the manufacture of tufted carpets, needle punch carpets, etc., mainly to prevent piles from falling off and to bond with secondary base fabrics such as jute. Therefore, this is one of the problems, and studies have been made to improve the formulation of copolymer latexes and compositions, but the reality is that so far no product of a satisfactory level has been obtained. [0009] Furthermore, adhesives have conventionally been manufactured by dissolving natural rubber, synthetic rubber, etc. in an organic solvent, coating it on a base material, and evaporating the organic solvent, but in recent years, the risk of fire has increased. Due to industrial and occupational health issues, there is increasing momentum to use polymer aqueous dispersions (latex) using water as a dispersion medium, and aqueous dispersions of rubber-tackifying resin combinations are being developed (Japanese Patent Publication No. 57-28545). JP-A-55-48270, JP-A-58-160378, JP-A-58-
183771). The aqueous dispersion containing the synthetic rubber latex and the tackifying resin generally has a composition in which 50 to 100 parts by weight of the tackifying resin is added to 100 parts by weight of the solid content of the latex, and the temperature is 20 to 23°C. Although it shows good adhesive physical properties at the measurement temperature of 0°C, a satisfactory value for adhesive strength at a temperature of 0°C is not obtained. In addition, there have been proposed products in which adhesive properties can be obtained only by using a rubber latex polymer without the presence of a tackifying resin (Japanese Patent Application Laid-Open Nos. 56-145909 and 57-57707). However, this material has the drawback of extremely low adhesion to polyethylene. [0010] [Problems to be Solved by the Invention] As described above, the conventional technology cannot cope with the further increase in printing speed of coated paper, but it is necessary to make it possible to manufacture high-quality coated paper. At present, there is a strong demand for the emergence of copolymer latex as a binder. Furthermore, copolymer latexes with high adhesive strength are similarly desired for carpets and adhesives. [0011]

[Means to solve the problem]

Under these circumstances, the present invention aims to improve the balance between pick strength and other properties in coated printing papers, as well as the adhesive strength of carpet pack sizing and adhesives. As a result of various studies aimed at providing a copolymer latex, we found that conventional radicals were used as chain transfer agents in the emulsion polymerization of conjugated dienes, ethylenically unsaturated carboxylic acids, and other monomers copolymerizable with these. Chain transfer agents or degree of polymerization regulators for polymerization reactions are well known (British Patent No. 725,869, JP-A-61-155413, JP-A-61-1).
A copolymer latex styrene obtained by using a dimer (A) of nuclear substituted α-methylstyrene (such as Japanese Patent Publication No. 34701) and a chain transfer agent (B) containing a sulfur element in a certain ratio. This was done after unexpectedly finding that the above objective was achieved. [0012] That is, the present invention uses a nuclear substituted α- shown in the following formula 2 as a chain transfer agent in emulsion copolymerization of a conjugated diene, an ethylenically unsaturated carboxylic acid, and other monomers copolymerizable with these. A combination of a methylstyrene dimer (A) and a chain transfer agent containing sulfur element (B) is used, and the usage ratio thereof is in the range of 2≦(A)÷(B)≦50. This is a method for producing copolymer latex. [0013)

[Formula 2] X-PhPh-X (where Ph is a benzene ring,
[0014] The present invention will be described in detail below. Addition of a chain transfer agent is a common and simple method for adjusting the gel fraction of latex to a desired level, but in emulsion polymerization for preparing the copolymer latex of the present invention, the nuclear device α - It is characterized by using a dimer of methylstyrene (A) and a chain transfer agent (B) containing elemental sulfur in a fixed ratio. [0015] Specific examples of the dimer (A) of nuclear substituted α-methylstyrene represented by the above formula 2 include 0-isopropenyltoluene, p-isopropenyltoluene, 2,3-dimethyl-α- Methylstyrene, 2,4-dimethyl-α-methylstyrene, 34-methyl-α-methylstyrene, p-
Isopropyl-α-methylstyrene, 2,6-dimethyl-4-tert-butyl-α-methylstyrene, O-chloro-α-methylstyrene, m-chloro-α-methylstyrene, p-chloro-α-methylstyrene, 2,5-dichloro-α-methylstyrene, 3,4-dichloro-α-
Methylstyrene, 31,5-dichloro-α-methylstyrene, 3-chloro-2-methyl-α-methylstyrene,
4-chloro-3-methyl-α-methylstyrene, 3-bromo-2-methyl-α-methylstyrene, 3-pro8-
4-methyl-α-methylstyrene, 3-fluoro-4-
Methyl-α-methylstyrene, p-chloromethyl-α-
Methylstyrene, 2,6-dimethoxy-α-methylstyrene, p-(2-chloroethoxy)-α-methylstyrene, 4-methyl-2-hydroxy-α-methylstyrene, p-glycidyl-α-methylstyrene, Examples include dimers such as 4-acetyl-α-methylstyrene, p-methylmercapto-α-methylstyrene, and p-ethylmercapto-α-methylstyrene. In the present invention, all of the dimers of the above-mentioned nuclear-substituted α-methylstyrene can be used, but preferred specific examples include 2,
Examples include 4-diphenyl-4-methyl-1-pentene and a mixture thereof with 2,4-diphenyl-4-methyl-2-pentene. [00161 Examples of the chain transfer agent (B) containing sulfur element include alkanethiols such as t-dodecylmercaptan and n-dodecylmercaptan; thioalkyl alcohols such as mercaptoethanol and mercaptopropanol; thioglycolic acid and thiopropionic acid. Thioalkylcarphonic acids such as: sulfides such as octyl-17thioglylate, dimethyl sulfide and diethyl sulfide; A preferable example of the chain transfer agent (B) containing the above-mentioned sulfur element is a thioalkylcarboxylic acid alkyl ester. [0017] The amounts of the dimer (A) of the nuclear substituted α-methylstyrene and the chain transfer agent (B) containing elemental sulfur are 2≦(A)÷(
B) It is necessary to be in the range of ≦50. The sum of the amounts of (A) and (B) used is preferably 0.05 to 10.0 parts by weight per 100 parts by weight of the monomer. If the blending weight ratio is less than 2 or more than 50, the effects of the present invention will not be exhibited satisfactorily. Although its function is not clear, it is thought to be due to the interaction of molecular terminal groups. [00183] Furthermore, the dimer (A) of nuclear substituted α-methylstyrene and the chain transfer agent (B) containing elemental sulfur can also be used in combination with other well-known chain transfer agents. Examples of other chain transfer agents include terpinolene, dipentene, t-
Mention may be made of halogenated hydrocarbons such as terpinene and carbon tetrachloride. Furthermore, any known method can be used for using the chain transfer agent. i.e. - pre-addition method;
These are a continuous addition method, an intermittent addition method, and a concentration gradient addition method in which the addition rate is sequentially changed. [0019] The latex polymer is obtained by emulsion copolymerization of monomers composed of a conjugated diene, an ethylenically unsaturated carboxylic acid, and other monomers copolymerizable with these. Conjugated dienes include butadiene, isoprene, 2-chloro-1,3-butadiene, and the like. The amount used is preferably in the range of 20 to 90% by weight based on the total monomers. Furthermore, in the case of a copolymer latex for coated paper, a more preferable range of the amount of this conjugated diene is 20 to 70% by weight.
It is. [00201 Examples of ethylenically unsaturated carboxylic acids include monobasic carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; dibasic carboxylic acids such as itaconic acid, maleic acid, and fumaric acid; and monoesters thereof. can be mentioned. The amount of ethylenically unsaturated carboxylic acid used is 0.5
It is preferably in the range of ~10% by weight. [0021] Among other monomers, aromatic (di)vinyl compounds are most typically and effectively used, followed by (meth)acrylic acid esters, vinyl cyanide compounds, and ethylenic amide monomers. etc. Examples of aromatic (di)vinyl compounds include styrene, α-methylstyrene, chlorostyrene, and alkylstyrene divinylbenzene. Examples of (meth)acrylic esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate.
Examples include meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, and ethylene glycol di(meth)acrylate. Examples of vinyl cyanide compounds include acrylonitrile and methacrylic nitrile. Ethylenic amide monomers include (meth)acrylamide, N-methylol (
Examples include meth)acrylamide. Besides that,
Vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides such as vinylidene chloride, aminoethyl (
Examples include ethylenic amine monomastyrene sulfonate sodium such as meth)acrylate, dimethylaminoethyl(meth)acrylate, and diethylaminoethyl(meth)acrylate. [0022] The production method of the present invention is produced by a conventionally known normal emulsion polymerization method. That is, in a dispersion system basically consisting of water, a surfactant, all monomers, a radical polymerization initiator, a chain transfer agent, and other raw materials if necessary, the monomer is made into an aqueous dispersion of polymer particles. In the manufacturing process, the polymer concentration generally ranges from 40 to 60% by weight. The particle size of the copolymer latex can be adjusted by the proportion of surfactant and/or seed latex used, and in general, the higher the proportion used, the smaller the particle size of the produced copolymer latex. [0023] Here, the preferred range of particle diameter is 0.05 to 1 μm, more preferably 0.07 to 0.5 μm. Examples of surfactants include fatty acid soaps, rosin acid soaps, anionic surfactants such as alkyl sulfonates, dialkylaryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, and polyoxyethylene alkylaryl sulfates. , polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester oxyethylene oxypropylene block copolymer, and other nonionic surfactants and cationic surfactants. The surfactant is usually used as an anionic surfactant alone or as a mixed anionic/nonionic system, and its usage ratio based on the total monomers is generally in the range of 0.05 to 2% by weight. [0024] The polymerization initiator is one that initiates addition polymerization of monomers by radical decomposition in the presence of heat or a reducing substance,
Water-soluble or oil-soluble beroxonisulfates, peroxides,
Azobis compounds and the like are commonly used. Examples include potassium peroxodi'fJR, sodium peroxodisulfate, ammonium peroxodisulfate hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, and cumene hydroperoxide. , and sometimes beroxonisulfate is most preferably used. The proportion of the polymerization initiator used is usually 0.2 to 1.5% by weight based on the total monomers. The polymerization temperature is generally in the range of 60 to 90°C. If you want to accelerate the polymerization rate or polymerize at a lower temperature, use sodium bisulfite, ascorbic acid or its salts, erythorbic acid or its salts, Rongalite, etc. A reducing agent is used in combination with a polymerization initiator.
A so-called redox polymerization method can be used. [00253] Also, various polymerization regulators are often added as desired. For example, sodium hydroxide,
These include pH adjusting agents such as potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, and disodium hydrogen phosphate, and various chelating agents such as sodium ethylenediaminetetraacetate. The copolymer latex of the present invention can be used as a binder for paper coating materials in a conventional manner. That is, the copolymer latex is mixed with an inorganic pigment and/or organic pigment, a water-soluble polymer, and various additives in water in which a dispersant is dissolved to form a uniform dispersion. 1. This paint can be applied to base paper using various methods such as a blade coater or a roll coater. [0026]

【Example】

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples. In addition, each characteristic was calculated|required as follows. (1) Properties of copolymer latex (a) Average particle size Light scattering particle size analyzer (Model 600 manufactured by CN Wood)
The average particle diameter of the copolymer latex was measured using 0). [0027] (b) Gel fraction of copolymer The copolymer latex was uniformly coated on a polypropylene film using a No. 26 wire bar, and dried for 1 hour in a dryer at 50° C. to form a film. . Next, this copolymer latex film was peeled off, approximately 0.5 g was accurately weighed using an analytical balance, and the mixture was immersed in a container containing 300 ml of toluene, and stirred at room temperature for 6 hours using a shaker. 45μm mesh with pre-measured contents
Filter through a wire mesh. Thereafter, it is dried in a drying oven at 50° C. for 2 hours, and the gel fraction is determined using the following formula. [0028]

[Equation 1] [0029] (2) Paper coating performance (a) Blister resistance Printing ink (WebbZett yellow, manufactured by Dainippon Ink Co., Ltd.) on both sides of the coated paper using an RI printing tester (manufactured by Mei Seisakusho) 0
．． Brush it all over with 3ml. This printed coated paper is cut to an appropriate size, and the test piece is immersed in a silicone oil constant temperature bath adjusted to a predetermined temperature to observe whether or not blisters occur. This test is performed by varying the temperature of the thermostatic chamber, and the lowest temperature at which blistering is observed is determined. The higher the temperature, the better the blister resistance. [00301 (b) Dry Pick Strength Using a RI printing tester, printing ink (SD Susu--Deluxe 50 Beni B; tack value 18, manufactured by Toka Shiki Co., Ltd.) 0.
Overprint 4m 15 times, trace the picking state that appears on the rubber roll onto another mount, and observe the degree of picking. Evaluation was performed using a 10-point evaluation method, and the fewer the picking phenomenon, the higher the score. [0031] (c) Wet pick strength RI printing test, using a parking machine, the surface of the coated paper was moistened with a water absorption roll, and then printing ink (SD Soot - Deluxe 50
Red B; tack value 18, manufactured by Toka Shiki Co., Ltd.) 0.4 m 11 times are printed, and the picking state that appears on the rubber roll is reversed onto another mount and the extent of the picking is observed. Evaluation was performed using a 10-point evaluation method, and the fewer the picking phenomenon, the higher the score. [0032] (d) Halftone dot reproducibility Printing was performed using a Ministry of Finance type gravure tester, and the halftone dot missing rate was counted. Evaluation was performed using a 10-point evaluation method, and the smaller the missing rate, the higher the score. (3) Carpet Pack Sizing Performance Peel strength and thread removal strength were determined in accordance with JIS L-1021. The higher the average value, the better. (4) Adhesive performance (a) High temperature cohesive force Place an adhesive sample on a stainless steel plate with a size of 25 mm x 25 mm.
Paste it by moving a 2 kg roller back and forth once with the size of
Set the adhesive surface parallel to the tensile direction of the tensile tester, and
The shearing force was measured at a speed of 2 mm/min in an atmosphere of .degree. [0033] (B) Low-temperature adhesive strength A loop was made with the adhesive layer of an adhesive sample having a width of 25 mm and a length of 250 mm facing up, and the loop was formed for 500 m in an atmosphere of 0°C.
It is brought into contact with the cardboard surface at a speed of m/min with almost no pressure. 3 seconds after contact, same < 50
The peel adhesive strength was measured when peeling off at a speed of 0 mm/min. [0034] (c) PE adhesive strength In an atmosphere of 23° C., an adhesive sample with a diameter of 25 mm was pasted on a low-density PE board that did not contain additives by moving it back and forth once with a 2 kg roller. After minutes had passed, the 180° peel strength was measured at a speed of 500 mm/min. [0035]

[Examples and comparative examples]

4 parts by weight of an aqueous dispersion of seed particles with a diameter of 0.04 μm (seed solid content concentration 25% by weight) was placed in a pressure-resistant reaction vessel equipped with a stirring device and a temperature control jacket, and 70 parts by weight of water and sodium lauryl sulfate were added. 0.2 parts by weight and 2.5 parts by weight of itaconic acid were charged, the internal temperature was raised to 80°C, and then an oily mixture consisting of the monomers and chain transfer agents shown in Tables 1, 2 and 3, and 15 parts by weight of water were added. parts, sodium beroxonisulfate 1 part by weight, sodium hydroxide 0.
An aqueous solution consisting of 2 parts by weight and 0.1 part by weight of sodium uralyl sulfate were added at a constant flow rate over 4 hours and 5 hours, respectively. After maintaining the temperature at 80°C for 1 hour, it was cooled, and the resulting copolymer latex was adjusted to pH 7 with sodium hydroxide, and unreacted monomers were removed by steam stripping. , and filtered through a filter cloth with a mesh size of 75 μm. Note that all copolymer latexes were adjusted so that the final solid content concentration was 50% by weight. [0036] [0037]

Application Example 1 The copolymer latexes prepared in Examples and Comparative Examples were evaluated for their performance as binders for paper coating. The results are shown in Table 6. The coating paint has the formulation shown in Table 4, and the nonvolatile content concentration is 6.
It was prepared in a high speed stirrer with a water content of 3% by weight. The pH of the paint was adjusted to 9.0 with aqueous ammonia. Table 5 shows the conditions for preparing coated paper using this paint. [0038] From Table 6, it is understood that the coated paper using the copolymer latex of the present invention as a binder has a highly balanced pick strength and other physical properties. [0039]

[Application Example 2] The copolymer latexes prepared in Examples and Comparative Examples were evaluated for their performance as binders for carpet pack sizing. The results are shown in Table 9. The adhesive paint has the formulation shown in Table 7 and has a nonvolatile content concentration of 7.
It was prepared in a high speed stirrer with a water content of 0% by weight. Table 8 shows the conditions for preparing Carpella I using this paint. [00401 Table 9 shows that the carpet using the copolymer latex of the present invention as a binder has highly improved peel strength and thread removal strength. [0041]

[Application Example 3] The copolymer latexes prepared in Examples and Comparative Examples were evaluated for their performance as adhesives. The results are shown in Table 10. Adhesive samples were created by the method shown below. Approximately 0.0% sodium polyacrylate was added to the resulting copolymer latex.
5 parts by weight was added to adjust the viscosity to about 10.0 OO cps, and after uniformly coating on release paper at a coating weight of about 45 dry g/m2, it was dried with hot air at 120° C. for 2.5 minutes. The resulting dried coating film on the release paper was pressed onto the corona discharge treated surface of a stretched polypropylene film (thickness: approximately 80 μm), and the dried coating film was transferred to the polypropylene film to prepare an adhesive sample. Adhesive sample temperature: 23℃, relative temperature: 65%
After curing for one week under these conditions, the adhesive properties were measured. [0042] Table 10 shows that the pressure-sensitive adhesive samples using the copolymer latex of the present invention have highly improved high-temperature cohesive strength, low-temperature adhesive strength, and PE adhesive strength. [0043]

[Table 1]

[Table 2]

[Table 3]

[Table 4] Engelhard [Ultra White 90] Engelhard [Ultra Coat] Mitsui Seifun Co. [Nisscalon #1500J Toagosei Kagaku [Aron T-404] Sumitomo Iji Maroshi [Sumilets 636] Japanese Food Products Kakosha rMs 4600J [0047]

[Table 5] [0048]

[Table 6] [0049]

[Table 7] 2) Toagosei Kagaku Co., Ltd. “Aron T-40J3) Kuraray Co. rPVA-217J [0050]

[Table 8]

[Table 9] [0052]

[Table 101 [0053] Effects of the Invention According to the present invention, the present invention provides high performance that can further improve the balance between pick strength and other performances in printed coated paper, and the adhesive strength in carpet back sizing and adhesives. copolymer latex can be easily obtained.

Claims (1)

[Claims] Claim 1: In the emulsion copolymerization of a conjugated diene, an ethylenically unsaturated carboxylic acid, and other monomers copolymerizable with these, a chain transfer agent consisting of a nucleus-substituted α-methylstyrene compound represented by the following formula 1 is used as a chain transfer agent. A copolymer latex characterized in that a polymer (A) and a chain transfer agent (B) containing an elemental sulfur are used in combination, and the usage ratio thereof is in the range of 2≦(A)÷(B)≦50. manufacturing method. [Chemical 1] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, Ph is a benzene ring, X and Y are hydrogen, halogen, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a hydroxyl group, a glycidyl group, acetyl group,
is an alkylmercapto group)