Process for preparing emulsion polymers having a hollow structure
First Claim
1. A process for preparing hollow polymer particles having a uniform hollow center and a uniform shell thickness, which comprises(1) a seed-forming step in which a monomer mixture consisting of (i) an acid monomer having a carboxylic acid group, and (ii) a non-ionic hydrophilic monomer is polymerized in the presence of a polymerization initiator to form a seed latex;
- (2) a core-forming step for preparing core particles in which a monomer mixture of (i) an acid monomer having a carboxylic acid group, (ii) a non-ionic hydrophilic monomer, and (iii) a cross-linking agent is emulsion polymerized on the seed latex to form a hydrophilic core;
(3) a shell-forming step in which a hydrophobic shell is formed on the hydrophilic core; and
in the shell-forming step (I) an emulsion comprising an emulsifier, water, and a monomer mixture of (i) up to 10 wt % of at least one acid monomer having a carboxylic acid group, (ii) 85 to 100 wt % of at least one non-ionic hydrophilic monomer, and (iii) up to 5 wt % of a cross-linking agent, and (II) an emulsion comprising an emulsifier, water, and a monomer mixture of (i) 95 to 100 wt % of at least one hydrophobic monomer and (ii) up to 5 wt % of a cross-linking monomer, are used in a ratio of 1/1 to 1/10 (emulsion (I)/emulsion (II)), the total amount of the monomer mixture in emulsion (I) and emulsion (II) being at least two times the weight of the core particles,carrying out the polymerization by continuously adding emulsion (II) dropwise to emulsion (I) and, at the same time, adding emulsion (I), partially containing emulsion (II), together with a water-soluble polymerization initiator to the core latex at the same rate as emulsion (II) is added to emulsion (I), to form a final latex, andswelling the final latex with an alkaline solution.
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Abstract
A process for preparing hollow polymer particles which comprises a seed-forming step for polymerizing a monomer mixture of an acid monomer having a carboxylic acid group and a non-ionic hydrophilic monomer in the presence of a polymerization initiator; a core-forming step for preparing a core, which can be swollen with an alkali, by polymerizing the monomer mixture of an acid monomer having a carboxylic acid group, a non-ionic hydrophilic monomer and a cross-linking agent to the seed latex; a shell-forming step in which a hydrophobic shell is formed on the hydrophilic core; and an alkali-swelling step.
74 Citations
12 Claims
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1. A process for preparing hollow polymer particles having a uniform hollow center and a uniform shell thickness, which comprises
(1) a seed-forming step in which a monomer mixture consisting of (i) an acid monomer having a carboxylic acid group, and (ii) a non-ionic hydrophilic monomer is polymerized in the presence of a polymerization initiator to form a seed latex; -
(2) a core-forming step for preparing core particles in which a monomer mixture of (i) an acid monomer having a carboxylic acid group, (ii) a non-ionic hydrophilic monomer, and (iii) a cross-linking agent is emulsion polymerized on the seed latex to form a hydrophilic core; (3) a shell-forming step in which a hydrophobic shell is formed on the hydrophilic core; and
in the shell-forming step (I) an emulsion comprising an emulsifier, water, and a monomer mixture of (i) up to 10 wt % of at least one acid monomer having a carboxylic acid group, (ii) 85 to 100 wt % of at least one non-ionic hydrophilic monomer, and (iii) up to 5 wt % of a cross-linking agent, and (II) an emulsion comprising an emulsifier, water, and a monomer mixture of (i) 95 to 100 wt % of at least one hydrophobic monomer and (ii) up to 5 wt % of a cross-linking monomer, are used in a ratio of 1/1 to 1/10 (emulsion (I)/emulsion (II)), the total amount of the monomer mixture in emulsion (I) and emulsion (II) being at least two times the weight of the core particles,carrying out the polymerization by continuously adding emulsion (II) dropwise to emulsion (I) and, at the same time, adding emulsion (I), partially containing emulsion (II), together with a water-soluble polymerization initiator to the core latex at the same rate as emulsion (II) is added to emulsion (I), to form a final latex, and swelling the final latex with an alkaline solution. - View Dependent Claims (2, 3, 4, 5, 7, 8, 9, 10, 11, 12)
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6. The process for preparing hollow polymer particles according to claim 13, wherein the acid monomer is selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, fumaric acid and iraconic acid.
Specification