Emulsion pressure-sensitive adhesive and process for producing the same

A process for producing an emulsion pressure-sensitive adhesive, which process comprises (co)polymerizing a monomer having a polymerizable unsaturated bond based on alkyl acrylates as a main component in an aqueous medium containing a surface active agent in the presence of a protective colloid, the protective colloid being an acrylic copolymer consisting of:

• (A-2) a hydrophilic monomer being acrylic acid and/or methacrylic acid;
• and
• (B-2) an alkyl (meth)acrylate that is copolymerizable with the hydrophilic monomer (A-2) and whose alkyl group has 4 to 9 carbon atoms;
• the hydrophilic monomer and the alkyl (meth)acrylate being copolymerized in a weight ratio in the range of 40-70:60-30;
• the acrylic copolymer having a weight-average molecular weight in the range of 500 to 50000.

A process for producing an emulsion pressure-sensitive adhesive, which process comprises (co)polymerizing a monomer having a polymerizable unsaturated bond based on alkyl acrylates as a main component in an aqueous medium containing a surface active agent in the presence of a protective colloid, the protective colloid being an acrylic copolymer consisting of:

• (A-2) a hydrophilic monomer being acrylic acid and/or methacrylic acid;
• (B-2) an alkyl (meth)acrylate that is copolymerizable with the hydrophilic monomer (A-2) and whose alkyl group has 4 to 9 carbon atoms;
• and
• (C) a third monomer being acrylonitrile and/or styrene;
• the hydrophilic monomer, the alkyl (meth)acrylate and the third monomer being copolymerized in a weight ratio (A-2):[(B-2)+(C)] in the range of 40-70:60-30 and in a weight ratio (B-2):(C) in the range of 99.9-20:0.1-80;
• the acrylic copolymer having a weight-average molecular weight in the range of 500 to 50000.

An emulsion pressure-sensitive adhesive comprising an aqueous medium and a (co)polymer dispersed in the aqueous medium, the (co)polymer being obtained by (co)polymerizing a monomer having a polymerizable unsaturated bond based on alkyl acrylates as a main component in an aqueous medium containing a surface active agent in the presence of a protective colloid, the protective colloid being an acrylic copolymer consisting essentially of:

• (A-1) at least one hydrophilic monomer selected from the group consisting of acrylamide, methacrylamide, hydroxyethyl acrylate and hydroxyethyl methacrylate;
• (B-1) an alkyl (meth)acrylate that is copolymerizable with the hydrophilic monomer (A-1) and whose alkyl group has 4 to 18 carbon atoms;
• and
• (C) a third monomer being acrylonitrile and/or styrene;
• the hydrophilic monomer, the alkyl (meth)acrylate and the third monomer being copolymerized in a weight ratio (A-1):[(B-1)+(C)] in the range of 40-70:60-30 and in a weight ratio (B-1):(C) in the range of 99.9-20:0.1-80;
• the acrylic copolymer having a weight-average molecular weight in the range of 500 to 50000.

An emulsion pressure-sensitive adhesive comprising an aqueous medium and a (co)polymer dispersed in the aqueous medium, the (co)polymer being obtained by (co)polymerizing a monomer having a polymerizable unsaturated bond based on alkyl acrylates as a main component in an aqueous medium containing a surface active agent in the presence of a protective colloid, the protective colloid being an acrylic copolymer consisting of:

• (A-2) a hydrophilic monomer being acrylic acid and/or methacrylic acid;
• and
• (B-2) an alkyl (meth)acrylate that is copolymerizable with the hydrophilic monomer (A-2) and whose alkyl group has 4 to 9 carbon atoms;
• the hydrophilic monomer and the alkyl (meth)acrylate being copolymerized in a weight ratio in the range of 40-70:60-30;
• the acrylic copolymer having a weight-average molecular weight in the range of 500 to 50000.

An emulsion pressure-sensitive adhesive comprising an aqueous medium and a (co)polymer dispersed in the aqueous medium, the (co)polymer being obtained by (co)polymerizing a monomer having a polymerizable unsaturated bond based on alkyl acrylates as a main component in an aqueous medium containing a surface active agent in the presence of a protective colloid, the protective colloid being an acrylic copolymer consisting of:

• (A-2) a hydrophilic monomer being acrylic acid and/or methacrylic acid;
• (B-2) an alkyl (meth)acrylate that is copolymerizable with the hydrophilic monomer (A-2) and whose alkyl group has 4 to 9 carbon atoms;
• and
• (C) a third monomer being acrylonitrile and/or styrene;
• the hydrophilic monomer, the alkyl (meth)acrylate and the third monomer being copolymerized in a weight ratio (A-2):[(B-2)+(C)] in the range of 40-70:60-30 and in a weight ratio (B-2):(C) in the range of 99.9-20:0.1-80;
• the acrylic copolymer having a weight-average molecular weight in the range of 500 to 50000.