JP2000154496A5 - - Google Patents

Description

[Claims]
1. (a) 10 to 80 parts by weight of a conjugated diene-based monomer, (b) 0.5 to 15 parts by weight of an ethylene-based unsaturated carboxylic acid monomer, and (c) the above-mentioned (a) conjugated diene. 5 to 89.5 parts by weight of the system monomer and the other monomer copolymerizable with the ethylene-based unsaturated carboxylic acid monomer (here, (a), (b) and (c) The total amount is 100 parts by weight . ) Containing a copolymer obtained by emulsifying and polymerizing in an aqueous medium, and having a toluene insoluble content of 80% by weight or more, a copolymer latex for paper coating. ..
2. In the molecular weight distribution obtained from the gel permeation chromatography measurement of the above-mentioned copolymer, the proportion of components detected earlier than the elution time corresponding to 1.1 million in polystyrene-equivalent molecular weight is 50% or more. The copolymer latex for paper coating according to claim 1, wherein the copolymer latex is characterized by this.
3. The copolymer latex for paper coating according to claim 1 or 2, which is used for coated paper for offset rotary printing.
Wherein 30 to 100% by weight of calcium carbonate and 0-70% by weight pigment other than calcium carbonate (wherein total of both is 100% by weight.) And pigment 100 parts by weight consisting of, claim 1 or A composition for paper coating, which comprises 1 to 30 parts by weight (in terms of solid content) of the copolymer latex according to claim 2.
5. The paper coating composition according to claim 4, which is used for offset rotary printing coated paper.

0002.
[Conventional technology]
Conventionally, a paper coating composition mainly composed of pigment and aqueous binder is applied to paper, excellent coated paper printability is prepared. Copolymer latex is used as a main binder in paper coating compositions because of its excellent adhesive strength.

In recent years, as printing has become more sophisticated and faster, the performance required for coated paper has become stricter, and improvements such as stickiness prevention, blister resistance, blank paper gloss, and printing gloss have been required. It was. Furthermore, in recent years there is an increasing demand to reduce the amount of the binder for the purpose of cost reduction, the binder exhibits sufficient surface strength even with a small amount of added weight than for this is required.

For copolymer latex, the nature, particularly the improvement of the surface strength is required, an improved method, such as adjusting the method and copolymers composition to adjust the gel content of the order, for example, copolymers have been proposed ing. However, surface strength and other properties often conflict with each other, and it is very difficult to achieve a high level of all properties in a well-balanced manner.

0008
[Problems to be Solved by the Invention]
An object of the present invention is that the surface strength and blister resistance of coated paper are significantly improved, and the gloss of blank paper and printing is excellent, and the mechanical stability and anti-stickiness are improved to improve the operability of coating. It is an object of the present invention to provide a copolymer latex suitable for paper coating, particularly for coating high-speed offset rotary printing paper. Another object of the present invention is to provide a composition for paper coating using the above-mentioned copolymer latex.

0009
[Means for solving problems]
According to the present invention, the following copolymer latex for paper coating is provided, and the above object of the present invention is achieved.
(1) (a) 10 to 80 parts by weight of a conjugated diene-based monomer, (b) 0.5 to 15 parts by weight of an ethylene-based unsaturated carboxylic acid monomer, and (c) the above-mentioned (a) conjugated diene-based single Quantities and other monomers copolymerizable with (b) ethylene-based unsaturated carboxylic acid monomers 5 to 89.5 parts by weight (here, the total amount of (a), (b) and (c)) is 100 parts by weight.) the include a copolymer obtained by emulsion polymerization in an aqueous medium, the paper coating copolymer latex, characterized in that toluene-insoluble matter is 80 wt% or more.
(2) In the molecular weight distribution obtained from the gel permeation chromatography measurement of the above copolymer, the proportion of components detected earlier than the elution time corresponding to 1.1 million in polystyrene-equivalent molecular weight is 50% or more. The copolymer latex for paper coating according to the above (1).
(3) The copolymer latex for paper coating according to (1) or (2) above, which is used for coated paper for offset rotary printing.
(4) 30 to 100% by weight of calcium carbonate and 0-70% by weight pigment other than calcium carbonate (wherein total of both is 100% by weight.) And pigment 100 parts by weight consisting of the above (1) or ( A composition for paper coating, which contains 1 to 30 parts by weight (in terms of solid content) of the copolymer latex according to 2).
(5) The paper coating composition according to (4) above, which is used for offset rotary printing coated paper.

When the toluene insoluble content of the copolymer latex for paper coating of the present invention is 80% by weight or more in terms of solid content, the above-mentioned desired performance of the present invention can be obtained. That is, since the copolymer latex of the present invention has a toluene insoluble content of 80% by weight or more, it has resistance to extremely large deformation, for example, during high-speed printing, and therefore has high adhesive strength. Furthermore, since the air permeability in the coating layer is maintained at an appropriate level, it also has excellent blister resistance. Further, since the copolymer latex of the present invention has a large amount of toluene insoluble , it has a small amount of low molecular weight components and is excellent in mechanical stability and anti-stickiness. Further, it has good blank paper gloss and high solvent resistance, so that it has high printing gloss. As described above, until now, blister resistance, mechanical stability and print gloss are contradictory performances, and it has not been possible to achieve both of these, but the toluene insoluble content of the present invention is 80% by weight or more. The polymer latex has made it possible to achieve both.

Specific examples of the (a) conjugated diene-based monomer used in the production of the copolymer latex for paper coating include butadiene, isoprene, 2- chloro -1,3-butadiene, and 2-methyl-1,3-. Butadiene and the like can be mentioned. These can be used alone or in combination of two or more. Of these, butadiene is particularly preferable.

(C) Other monomer copolymerizable with (a) conjugated diene-based monomer and (b) ethylene-based unsaturated carboxylic acid monomer (hereinafter, also referred to as "(c) other monomer"). Specific examples of (referred to as) include (a) ethyl acrylate, butyl acrylate, -2-ethyl hexyl acrylate, methyl methacrylate, hexyl methacrylate, octyl methacrylate, -2-ethyl hexyl methacrylate, and the like. Acryloacid such as lauryl methacrylate and glycidyl methacrylate or alkyl ester of methacrylic acid, or glycidyl ester, aromatic vinyl compounds such as (b) styrene, α-methylstyrene, vinyltomer and p-methylstyrene, (c) acrylamide. , Methacrylic acid, N, N-dimethylacrylamide, N-methylolacrylamide and other ethylene-based unsaturated carboxylic acid acrylamide or methacrylic acid compounds, (d) Vinyl acetate and other carboxylic acid vinyl esters, (e) Acrylonitrile, Methacrylic acid Examples thereof include vinyl cyanide compounds such as nitrile and α- chloroacrylonitrile. These can be used alone or in combination of two or more. Of these, styrene as an aromatic vinyl compound and acrylonitrile as a vinyl cyanide compound are particularly preferably used.

As described above, the copolymer latex for paper coating of the present invention has a toluene insoluble content of 80% by weight or more. The toluene insoluble content of the copolymer latex of the present invention is a value measured as follows. That is, after adjusting the copolymer latex to pH 7.5, it is coagulated with isopropanol, then the coagulated product is washed with methanol and dried, and then a predetermined amount (about 0.05 g) of a sample is prepared in a predetermined amount (100 ml). Soak in toluene for 20 hours. After that, No. Filter with the qualitative filter paper of No. 2, and the weight% of the remaining solid content on the obtained filter paper with respect to the total solid content is defined as the toluene insoluble content. The above-mentioned toluene insoluble content can be controlled by the polymerization temperature, the amount of the molecular weight modifier, the method of adding the monomer, and the like.
The toluene insoluble content of the copolymer latex in the present invention is 80% by weight or more, preferably 85 to 100% by weight, more preferably 90 to 100% by weight, still more preferably 91 to 100% by weight, and particularly preferably 94 to 100% by weight. %. If the toluene insoluble content is less than 80% by weight, the blister resistance or dry strength is lowered, and the mechanical stability and stickiness prevention property are also lowered.

In the present invention, GPC is measured under the following conditions.
<Sample preparation >
To 0.3 g of the copolymer latex having a solid content adjusted to 48% by weight, 1 g of water and about 1 g of a cation exchange resin washed and washed with water according to a conventional method are added to remove cations. Then, 50 ml of tetrahydrofuran is added and left for 2 hours to dissolve. Next , the mixture is filtered through a polytetrafluoroethylene membrane filter (pore size 3 μm, manufactured by ADVANTEC), and the filtrate is used as a measurement sample.
<Device, measurement conditions, etc.>
Measuring device: HLC-8020 (manufactured by Tosoh Corporation)
Filler type, particle size: polystyrene gel 30 μm
GMH HR-H (30 ) Made by Tosoh Corporation Column size: 7.8mm 2D x 300mm
Solvent: tetrahydrofuran Sample concentration: 0.3% by weight
Injection volume: 30 μl
Flow speed: 1 ml / min Temperature: 40 ° C
Detector: Differential refractometer In the measurement, a calibration curve was prepared in advance using a polystyrene standard substance having a known molecular weight, and the molecular weight was expressed as polystyrene equivalent.

In addition to calcium carbonate, kaolin clay, talc, barium sulfate, titanium oxide (rutile , anatase), aluminum hydroxide, zinc oxide, satin white, etc. should be used as the inorganic pigment, and polystyrene latex, etc. should be used as the organic pigment. Can be done. These can be used alone or in combination of two or more.
Specific examples of calcium carbonate used in the present invention include heavy calcium carbonate and light calcium carbonate.
These can be used alone or in combination of two or more, depending on the purpose.

The composition for paper coating using the copolymer latex for paper coating of the present invention can be applied by a conventionally known method, for example, using an air knife coater, a blade coater, a roll coater, an applicator or the like.

0045
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In addition, "%" and "part" in an Example are weight-based.
<Examples 1 and 2>
(Manufacturing method of copolymer latex)
After charging 0.1 part of seed latex containing carboxy-modified polystyrene having an average particle size of 30 nm, 150 parts of water, 0.3 part of sodium dodecylbenzenesulfonate, and 1.0 part of potassium persulfate in a 100-liter pressure-resistant container, In a nitrogen atmosphere, at a temperature of 70 ° C., 0.2 part of sodium dodecylbenzenesulfonate and the second-stage component shown in Table 1 were continuously added for 8 hours. Then, the reaction was continued for another 5 hours to complete the polymerization. The final polymerization conversion was 98%. The obtained copolymerized latex is adjusted to pH 7.5 using sodium hydroxide, then steam is blown to remove unreacted monomers, and further heated vacuum distillation is performed for paper coating with a solid content concentration of 50%. A copolymer latex was obtained.
The average particle size of the obtained copolymerized latex was determined by a conventional method using a particle size measuring device manufactured by Otsuka Electronics Co., Ltd. The toluene insoluble content of the copolymer latex was determined by the method described above. In the molecular weight distribution obtained from the GPC measurement of the copolymer contained in the copolymer latex, the proportion of the component detected faster than the elution time corresponding to 1.1 million in the polystyrene-equivalent molecular weight was also determined by the method described above. The results are shown in Table 5.

(Preparation of composition for paper coating)
By using the copolymer latex prepared above, the paper coating composition of web offset printing was prepared by the following formulation.
Formulation;
Kaolin Clay 50.0 parts Calcium carbonate 50.0 parts Dispersant 0.2 parts Sodium hydroxide 0.1 parts Starch 4.0 parts Latex (as solid content) 10.0 parts Water Total solid content should be 60% Add an appropriate amount to

This paper coating composition is coated on the coating base paper with an electric blade coater ( manufactured by Kumagai Riki Kogyo Co., Ltd.) so that the coating ^{amount is 18.0 ± 0.5 g / m 2.} It was dried for 15 seconds in an electric hot air dryer at 150 ° C. The obtained coated paper was left in a constant temperature and humidity chamber having a temperature of 23 ° C. and a humidity of 50% for one day and night, and then super calendar treatment was performed four times under the conditions of a linear pressure of 100 kg / cm and a roll temperature of 50 ° C. The performance of the obtained coated paper was evaluated by the following method.
(1) Dry pick strength The degree of picking when printed by an RI printing machine was judged with the naked eye and evaluated on a 5-point scale. The less the picking phenomenon, the higher the score. The numerical value is shown as an average value of 6 measurements.
(2) Wet Pick Strength Using an RI printing machine, the surface of the coated paper was moistened with a water-absorbing roll, and then the degree of picking when printing with the RI printing machine was visually judged and evaluated on a 5-point scale. The less the picking phenomenon, the higher the score. The numerical value is shown as an average value of 6 measurements.
(3) Blister resistance After adjusting the humidity (about 6%) of the double-sided printing coated paper, it was put into a heated oil bath, and the minimum temperature at which blister was generated was shown.
(4) Printing gloss The offset ink was solidly applied using an RI printing machine, and the measurement was performed at an angle of 60 degrees using a Murakami type gloss meter.
(5) Anti-stickiness Latex was applied to polyethylene terephthalate film No. It is applied with an 18 rod and dried at 120 ° C. for 30 seconds to form a film. This film and Kurora paper are combined and crimped with a bench super calendar under the conditions of a linear pressure of 200 kg / m and a temperature of 70 ° C. Both are peeled off, and the degree of transfer of Kurorasha paper to latex is visually evaluated on a 5-point scale. The less the transcription, the higher the score. The numerical value is shown as an average value of 6 measurements.
(6) Mechanical stability Using a commercially available malon-type mechanical stability tester, a copolymer latex (solid content concentration 30% by weight, sample 120 g) is coated with a rotor rotation speed of 1000 rpm, a rotor load of 15 kg , and a rotation time. After mechanical shearing under 15 minute conditions, the agglomerates remaining on the 120 mesh wire mesh were captured. After the captured agglomerates were dried, the ratio of the agglomerates to the original sample solid content weight was determined by weight%. The results of evaluation by the above evaluation method are shown in Table 5.

<Examples 3 and 4>
After charging 150 parts of water, 0.1 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate, and the first-stage components shown in Table 1 in a 100-liter pressure-resistant container, the temperature is 70 in a nitrogen atmosphere. Polymerization was carried out at ° C. for 2 hours. Next, the second-stage components shown in Table 1 were continuously added for 8 hours. Then, the reaction was continued for another 5 hours to complete the polymerization. The final polymerization conversion was 98%. The obtained copolymer latex was pH- adjusted and concentrated in the same manner as in Example 1.
In the average particle size, toluene insoluble matter, and molecular weight distribution obtained from GPC measurement of the obtained copolymerized latex, the proportion of components detected faster than the elution time corresponding to 1.1 million in polystyrene equivalent molecular weight is defined as Example 1. Obtained in the same way. The results are shown in Table 5. The preparation of the composition for paper coating, the preparation of the coated paper, and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Table 5.

<Examples 5 and 6>
In a 100 liter pressure-resistant container, 150 parts of water, 0.5 part of sodium dodecylbenzenesulfonate, 0.8 part of potassium persulfate, and the first-stage components shown in Tables 1 and 2 were charged, and then in a nitrogen atmosphere. Polymerization was carried out at a temperature of 70 ° C. for 15 hours. The final polymerization conversion rate was 98%. The obtained copolymer latex was pH- adjusted and concentrated in the same manner as in Example 1.
In the average particle size, toluene insoluble matter, and molecular weight distribution obtained from GPC measurement of the obtained copolymerized latex, the proportion of components detected faster than the elution time corresponding to 1.1 million in polystyrene equivalent molecular weight is defined as Example 1. Obtained in the same way. The results are shown in Tables 5 and 6. The preparation of the composition for paper coating, the preparation of the coated paper, and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Tables 5 and 6.

<Examples 7 and 8>
After charging 150 parts of water, 0.5 part of sodium dodecylbenzenesulfonate, 0.3 part of potassium persulfate, and the first-stage components shown in Table 2 in a 100-liter pressure-resistant container, the temperature is 60 in a nitrogen atmosphere. Polymerization was carried out at ° C. for 4 hours. Next, the second-stage components shown in Table 1 were collectively charged and polymerized for another 10 hours. The final polymerization conversion was 98%. The obtained copolymer latex was pH-adjusted and concentrated in the same manner as in Examples 1 and 2. In the average particle size, toluene insoluble matter, and molecular weight distribution obtained from GPC measurement of the obtained copolymerized latex, the proportion of components detected faster than the elution time corresponding to 1.1 million in polystyrene-equivalent molecular weight was determined in Example 1 . It was obtained by the same method as 2. The results are shown in Table 6. The preparation of the composition for paper coating, the preparation of the coated paper, and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Table 6.

<Examples 9, 10, 11, 12>
(Preparation of Paper Coating Compositions of Examples 9, 10, 11 and 12)
The procedure was the same as in Example 1 except that the following copolymer latex and pigment were used.
Pigment (part)
Copolymer Latex Calcium Carbonate Kaolin Clay Example 9 Latex of Example 1 60 40
Example 10 Latex of Example 2 60 40
Example 11 Latex 20 80 of Example 1
Example 12 Latex 20 80 of Example 2
The preparation of the coated paper and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Tables 6 and 7.

<Comparative Examples 1 and 2>
After charging 0.1 part of seed latex containing carboxy-modified polystyrene having an average particle size of 30 nm, 150 parts of water, 0.3 part of sodium dodecylbenzenesulfonate, and 1.0 part of potassium persulfate in a 100-liter pressure-resistant container, In a nitrogen atmosphere, at a temperature of 70 ° C., 0.2 part of sodium dodecylbenzenesulfonate and the second-stage component shown in Table 3 were continuously added for 8 hours. Then, the reaction was continued for another 5 hours to complete the polymerization. The final polymerization conversion was 98%.
The obtained copolymer latex was pH- adjusted and concentrated in the same manner as in Example 1.
In the average particle size, toluene insoluble matter, and molecular weight distribution obtained from GPC measurement of the obtained copolymerized latex, the proportion of components detected faster than the elution time corresponding to 1.1 million in polystyrene equivalent molecular weight is defined as Example 1. Obtained in the same way. The results are shown in Table 7. The preparation of the composition for paper coating, the preparation of the coated paper, and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Table 7.

<Comparative Examples 3 and 4>
After charging 150 parts of water, 0.1 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate, and the first-stage components shown in Table 3 in a 100-liter pressure-resistant container, the temperature is 70 in a nitrogen atmosphere. Polymerization was carried out at ° C. for 2 hours. Next, the second-stage components shown in Table 3 were continuously added for 8 hours. Then, the reaction was continued for another 5 hours to complete the polymerization. The final polymerization conversion was 98%. The obtained copolymer latex was pH- adjusted and concentrated in the same manner as in Example 1.
In the average particle size, toluene insoluble matter, and molecular weight distribution obtained from GPC measurement of the obtained copolymerized latex, the proportion of components detected faster than the elution time corresponding to 1.1 million in polystyrene equivalent molecular weight is defined as Example 1. Obtained in the same way. The results are shown in Tables 7 and 8. The preparation of the composition for paper coating, the preparation of the coated paper, and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Tables 7 and 8.

<Comparative Examples 5 and 6>
In a 100 liter pressure-resistant container, 150 parts of water, 0.5 part of sodium dodecylbenzenesulfonate, 0.8 part of potassium persulfate, and the first-stage components shown in Tables 3 and 4 were charged, and then in a nitrogen atmosphere. Polymerization was carried out at a temperature of 70 ° C. for 15 hours. The final polymerization conversion rate was 98%. The obtained copolymer latex was pH- adjusted and concentrated in the same manner as in Example 1.
In the average particle size, toluene insoluble matter, and molecular weight distribution obtained from GPC measurement of the obtained copolymerized latex, the proportion of components detected faster than the elution time corresponding to 1.1 million in polystyrene equivalent molecular weight is defined as Example 1. Obtained in the same way. The results are shown in Table 8. The preparation of the composition for paper coating, the preparation of the coated paper, and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Table 8.

<Comparative Examples 7 and 8>
After charging 150 parts of water, 0.5 part of sodium dodecylbenzenesulfonate, 0.3 part of potassium persulfate, and the first-stage components shown in Table 4 in a 100-liter pressure-resistant container, the temperature is 60 in a nitrogen atmosphere. Polymerization was carried out at ° C. for 4 hours. Next, the second-stage components shown in Table 4 were collectively charged and polymerized for another 10 hours. The final polymerization conversion was 98%. The obtained copolymer latex was pH- adjusted and concentrated in the same manner as in Example 1.
In the average particle size, toluene insoluble matter, and molecular weight distribution obtained from GPC measurement of the obtained copolymerized latex, the proportion of components detected faster than the elution time corresponding to 1.1 million in polystyrene equivalent molecular weight is defined as Example 1. Obtained in the same way. The results are shown in Table 8. The preparation of the composition for paper coating, the preparation of the coated paper, and the performance evaluation of the prepared coated paper were carried out in the same manner as in Example 1. The results of the coated paper evaluation are shown in Table 8.

As is clear from the results shown in Tables 5 to 8, the copolymer latex of Examples 1 to 12 has achieved the object of the present invention. This is because this copolymer latex has a toluene insoluble content of 80% by weight or more, and therefore has high resistance to extremely large deformation during high-speed printing, so that it exhibits high adhesive strength, and further, transparency in the coating layer. It is based on the fact that it has excellent blister resistance because its temperament is maintained at an appropriate level. On the other hand , the copolymer latex of Comparative Examples 1 to 8 has a small amount of toluene insoluble and is inferior in their performance, and also has a large amount of low molecular weight components, so that the stickiness prevention property and the printing gloss are also inferior.

[0065]
【Effect of the invention】
The copolymer latex for paper coating obtained by the present invention and the composition for paper coating using the same have properties that contradict the two properties of adhesive strength, blister resistance, stickiness prevention property, and printing gloss, which could not be achieved by the prior art. Are compatible with each other, and the balance of physical properties can be greatly improved. Furthermore, the mechanical stability is significantly improved, coating operability, printing operability, those having excellent characteristics printability, extremely high industrial value.