Title of Invention

METHOD FOR PREPARING STYRENE-BUTADIENE LATEX

Abstract The present invention relates to a method for preparing a styrene-butadiene latex, more particularly to a method for preparing a styrene-butadiene latex comprising the steps of adding a transition boosting agent to a styrene-butadiene copolymer, stirring the mixture and deodorizing the product. Since unreacted residual monomers and volatile organic compounds are reduced significantly, foul smell during drying at high temperature, irritation to skin and eyes and foul smell of the final product can be prevented.
Full Text

Description
METHOD FOR PREPARING STYRENE-BUTADIENE LATEX
Technical Field
[1] The present invention relates to a method for preparing a styrene-butadiene latex,
more particularly to a method for preparing a styrene-butadiene latex with no foul smell during drying at high temperature, no irritation to skin and eyes and no foul smell in the final product by significantly reducing residual monomers and volatile organic compounds.
Background Art
[2] In general, a styrene-butadiene latex is prepared by copolymerization. Typically, the
final yield is 95 % or above. Residual monomers and volatile organic compounds (VOC's) are removed from such prepared latex through a deodorization process, which is conventionally performed with steam.
[3] Despite the deodorization process, it is impossible to completely remove the
residual monomers and volatile organic compounds. When the materials are present in the latex in large amount, it smells bad when the latex is dried at high temperature and, in severe cases, skin and eye irritation may occur. The residual monomers and volatile organic compounds also cause foul smell of the final product.
[4] Up to now, extension of the deodorization process has been carried out in order to
reduce the residual monomers and volatile organic compounds. But, this method is limited in reducing the residual monomers and volatile organic compounds and increases the production time, thereby lowering productivity.
Disclosure of Invention Technical Solution
[5] It is an object of the present invention to provide a method for preparing a styrene-
butadiene latex with no foul smell during drying at high temperature, no irritation to skin and eyes and no foul smell in the final product by significantly reducing the residual monomers and volatile organic compounds.
[6] It is another object of the invention to provide a paper coating composition with no
foul smell and no irritation to skin and eyes and a paper treated with the same.
[7] To attain the objects, the present invention provides a method for preparing a
styrene-butadiene latex comprising the step of adding a transition boosting agent to a styrene-butadiene copolymer, stirring the mixture and deodorizing the product.
[8] The invention also provides a paper coating composition comprising such prepared
styrene-butadiene latex.
[9] The invention further provides a paper coated with the coating composition.

[10] Hereunder is given a detailed description of the present invention.
[11] The present inventors found that residual monomers and volatile organic
compounds can be significantly reduced from a latex when a transition boosting agent is added to a styrene-butadiene copolymer, because polymerization degree of the unreacted monomers and volatile organic compounds are increased.
[12] The styrene-butadiene latex of the present invention is prepared by adding a
transition boosting agent to a styrene-butadiene copolymer, stirring the mixture and deodorizing the product.
[13] The styrene-butadiene copolymer used in the invention can be prepared by a con-
ventional method.
[14] Specifically, the styrene-butadiene copolymer can be prepared by polymerizing a
styrene monomer, a butadiene monomer, an ethylenic unsaturated acid monomer, a vinyl cyanide monomer and a monomer copolymerizable with the afore-mentioned monomers in the presence of a chain transfer agent. More specifically, it may be prepared by polymerizing 20-90 parts by weight of a styrene monomer, 10-70 parts by weight of a butadiene monomer, 1-18 parts by weight of an ethylenic unsaturated acid monomer, 0.5-15 parts by weight of a vinyl cyanide monomer and 1-25 parts by weight of a monomer copolymerizable with the afore-mentioned monomers. Or, it can be prepared by polymerizing each monomer to form a seed, grafting the monomer in the seed to form a core and grafting the monomer in the core to form a shell.
[15] The styrene monomer offers adequate hardness and water repellency to the prepared
copolymer. Any conventional styrene monomer used to prepare a styrene-butadiene copolymer can be used.
[16] Preferably, the styrene monomer is comprised in 20-90 parts by weight per 100
parts by weight of the total monomers. If the content is below 20 parts by weight, hardness and water repellency may be insufficient. Otherwise, if it exceeds 90 parts by weight, adhesion force and film forming ability may worsen.
[17] The butadiene monomer offers flexibility to the prepared copolymer. Any con-
ventional butadiene monomer used to prepare a styrene-butadiene copolymer can be used. Preferably, 1,3-butadiene is used.
[181 Preferably, the butadiene monomer is comprised in 10-70 parts by weight per 100
parts by weight of the total monomers. If the content is below 10 parts by weight, the prepared copolymer becomes too hard. Otherwise, if it exceeds 70 parts by weight, rigidity decreases significantly.
[19] The ethylenic unsaturated acid monomer enhances adhesion force of the prepared
copolymer and improves stability of the copolymer particles.
[20] For the ethylenic unsaturated acid monomer, an unsaturated carboxylic acid or an
unsaturated polycarboxylic acid alkyl ester having at least one carboxylic acid group

may be used. Particularly, the unsaturated carboxylic acid may be methacrylic acid, acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, etc. And, the unsaturated polycarboxylic acid alkyl ester may be itaconic acid monoethyl ester, fumaric acid monobutyl ester, maleic acid monobutyl ester, etc.
[21] Preferably, the ethylenic unsaturated acid monomer is comprised in 1-18 parts by
weight per 100 parts by weight of the total monomers. If the content is below 1 part by weight, improvement of adhesion force and particle stability cannot be expected. Otherwise, if it exceeds 18 parts by weight, polymerization stability, etc. may be not good.
[22] The vinyl cyanide monomer improves print gloss.
[23] For the vinyl cyanide monomer, acrylonitrile or methacrylonitrile may be used.
Preferably, it is comprised in 0.5-15 parts by weight per 100 parts by weight of the total monomers.
[24] The monomer copolymerizable with the afore-mentioned monomers offers
adequate hardness to the prepared latex and improves film forming ability.
[25] For the copolymerizable monomer, methyl acry late, etc. may be used. Preferably, it
is comprised in 1-25 parts by weight per 100 parts by weight of the total monomers.
[26] The chain transfer agent is used to adjust molecular weight, gel content and gel
structure of the styrene-butadiene copolymer. Preferably, it is comprised in 0.1-5 parts by weight per 100 parts by weight of the total monomers.
[27] Further, such common additives as a polymerization initiator, an emulsifier, an
electrolyte, etc. may be added when preparing the styrene-butadiene copolymer.
[28] When the transition ratio to the styrene-butadiene copolymer reaches 80-99 %, a
transition boosting agent is added and the mixture is stirred.
[29] The transition boosting agent increases degree of polymerization of the unreacted
monomers and volatile organic compounds present in the styrene-butadiene copolymer, and thus reduces contents of the residual monomers and volatile organic compounds.
[30] For the transition boosting agent, a compound copolymer with the styrene-
butadiene copolymer can be used. Particularly, an unsaturated carboxylic acid alkyl ester such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, etc.; an unsaturated carboxylic acid hydroxyalkyl ester such as (β-hydroxyethyl acrylate, (β-hydroxypropyl acrylate, (β-hydroxyethyl methacrylate, etc.; an unsaturated carboxylic acid amide such as acrylamide, methacrylamide, itaconamide, maleic acid monoamide, etc. and derivatives thereof; or an aromatic vinyl monomer such as a-methylstyrene, vinyltoluene,p-methylstyrene, etc. are preferable.
[31] Preferably, the transition boosting agent is comprised in 0.1-20 parts by weight per

100 parts by weight of the styrene-butadiene copolymer. Within this range, reduction
of the residual monomers and volatile organic compounds is more effective.
[32] In addition, such polymerization initiator as potassium persulfate may be added
when adding the transition boosting agent. Preferably, it is comprised in 0.1-1 part by
weight.
[33] After the residual monomers and volatile organic compounds are removed, the
styrene-butadiene copolymer is deodorized as is done in the conventional method for
preparing a styrene-butadiene latex.
[34] The present invention also provides a paper coating composition comprising the
styrene-butadiene latex and a paper coated with the composition. The coating
composition and the paper do not give off foul smell during drying at high temperature
and cause no skin or eye irritation. Thus, processing thereof is convenient and the final
product does not have foul smell.
Best Mode for Carrying Out the Invention
[35] Hereinafter, the present invention is described further in detail through examples.
However, the following examples are only for the understanding of the invention and the invention is not limited to or by the following examples.
[36] [Examples]
[37] Example 1
[38] Air inside a 10 L pressurized reactor equipped with an stirrer, a thermometer, a
cooler and a nitrogen gas inlet, which is capable of feeding a monomer, an emulsifier and a polymerization initiator continuously, was replaced with nitrogen. After feeding 5 parts by weight of a styrene-butadiene seed, 33 parts by weight of butadiene, 49 parts by weight of styrene, 8 parts by weight of methyl methacrylate, 5 parts by weight of acrylonitrile, 5 parts by weight of itaconic acid, 3 parts by weight of sodium dode-cyldibenzensulfonate, 0.3 part by weight of r-dodecylmercaptan, 0.4 part by weight of sodium bicarbonate and 420 parts by weight of ion exchange water, the reactor was heated to 80 °C. 0.8 part by weight of potassium persulfate, a polymerization initiator, was added and polymerization was performed for about 300 minutes while stirring. The transition ratio of the copolymer was 91 %.
[39] To the prepared copolymer were added 10 parts by weight of methyl acrylate, a
transition boosting agent, and 0.2 part by weight of potassium persulfate, a polymerization initiator. After heating to 90 °C, the mixture was stirred for 360 minutes.
[40] After stirring, deodorization was performed for 360 minutes to obtain a styrene-
butadiene latex.
[41] Examples 2-10
[42] The procedure of Example 1 was repeated, except for using transition boosting



[56] . Table 4

[57]
[58] As seen in Table 4, when transition boosting agents were used according to the
present invention (Examples 1-12), contents of residual monomers and volatile organic compounds were significantly lower than those for Comparative Examples 1-3. When deodorization time was increased (Comparative Example 3), contents of residual monomers and volatile organic compounds could be reduced, but not so much as in Examples 1-12.
Industrial Applicability
[59] The present invention is advantageous in significantly reducing residual monomers
and volatile organic compounds, thereby preventing foul smell during drying at high temperature, irritation to skin and eyes and foul smell in the final product.
[60] While the present invention has been described in detail with reference to the
preferred embodiments, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the present invention as set forth in the appended claims.
Claims
[ 1 ] A method for preparing a styrene-butadiene latex comprising the steps of adding
a transition boosting agent to a styrene-butadiene copolymer, stirring the mixture and deodorizing the product.
[2] The method of claim 1, the styrene-butadiene copolymer being prepared by
polymerizing a styrene monomer, a butadiene monomer, an ethylenic unsaturated acid monomer, a vinyl cyanide monomer and a monomer copolymerizable with the afore-mentioned monomers in the presence of a chain transfer agent.
[3] The method of claim 1, the transition boosting agent being added when the
transition ratio of the styrene-butadiene copolymer is 80-99 %.
[4] The method of claim 1, the transition boosting agent being at least one selected
from a group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, (β-hydroxyethyl acrylate, (β-hydroxypropyl acrylate, (β-hydroxyethyl methacrylate, acrylamide, methacrylamide, itaconamide, maleic acid monoamide, a-methylstyrene, vinyltoluene and ;pmethylstyrene.
[5] The method of claim 1, the transition boosting agent being comprised in 0.1-20
parts by weight per 100 parts by weight of the styrene-butadiene copolymer.
[6] A paper coating composition comprising a styrene-butadiene latex prepared by
the method of claim 1.
[7] A paper coated with the coating composition of claim 6.
Dated this 15 day of December 2006

Documents:

4607-CHENP-2006 CORRESPONDENCE OTHERS.pdf

4607-CHENP-2006 CORRESPONDENCE PO.pdf

4607-CHENP-2006 FORM-3.pdf

4607-CHENP-2006 PETITIONS.pdf

4607-chenp-2006 abstract.pdf

4607-chenp-2006 claims.pdf

4607-chenp-2006 correrspondance others.pdf

4607-chenp-2006 others.pdf

4607-chenp-2006-abstract.pdf

4607-chenp-2006-claims.pdf

4607-chenp-2006-correspondnece-others.pdf

4607-chenp-2006-description(complete).pdf

4607-chenp-2006-form 1.pdf

4607-chenp-2006-form 26.pdf

4607-chenp-2006-form 3.pdf

4607-chenp-2006-form 5.pdf

4607-chenp-2006-form18.pdf

4607-chenp-2006-pct.pdf


Patent Number 240385
Indian Patent Application Number 4607/CHENP/2006
PG Journal Number 20/2010
Publication Date 14-May-2010
Grant Date 07-May-2010
Date of Filing 15-Dec-2006
Name of Patentee LG CHEM, LTD.
Applicant Address LG TWIN TOWERS EAST TOWER 20 YEOUIDO-DONG YEONGDEUNGPO-GU SEOUL 150-721 SEOUL 150-721 REPUBLIC OF KOREA
Inventors:
# Inventor's Name Inventor's Address
1 CHOI HO-YEUL 104-603 SEJONG APT JEONMIN-DONG YUSEONG-GU DAEJEON 305-728 KOREA
2 YANG SEUNG-HUN 107-902 CHOWON APT MANNYEON-DOMG SEO-GU DAEJEON 302-740 KOREA
3 HAN CHANG-SUN 106-1101 DAELIM DURE APT, SINSEONG-DONG YUSEONG-GU DAEJEON 305-720 KOREA
PCT International Classification Number C08F6/06
PCT International Application Number PCT/KR05/03483
PCT International Filing date 2005-10-19
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10-2004-0084423 2004-10-21 Republic of Korea