Acrylic-type pressure sensitive adhesives by means of ultraviolet radiation curing

• US 4,181,752 A
• Filed: 09/25/1978
• Issued: 01/01/1980
• Est. Priority Date: 09/03/1974
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Martens, John A., Clemens, Lawrence M., Zigman, Alvin R.
• Primary Examiner(s): Turer, Richard B.
• Application Number:
  US05/945,406
• Time in Patent Office: 463 Days
• Field of Search: 204/159.14, 204/159.16, 204/159.22, 204/159.23, 204/159.24, 427/54
• US Class Current: 427/516
• CPC Class Codes: C08F 2/46 Polymerisation initiated by wave energy or particle radiation
• CPC Class Codes: C08F 20/18 with acrylic or methacrylic acids
• CPC Class Codes: C08F 220/10 Esters
• CPC Class Codes: C09J 4/00 Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
• CPC Class Codes: C09J 7/385 Acrylic polymers
• CPC Class Codes: Y10S 522/913 Numerically specified distinct wavelength
• CPC Class Codes: Y10S 526/931 Pressure sensitive adhesive
• CPC Class Codes: Y10T 428/2887 including nitrogen containing polymer [e.g., polyacrylonitrile, polymethacrylonitrile, etc.]
• CPC Class Codes: Y10T 428/2891 including addition polymer from alpha-beta unsaturated carboxylic acid [e.g., acrylic acid, methacrylic acid, etc.] Or derivative thereof
• CPC Class Codes: Y10T 428/31797 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31884 Regenerated or modified cellulose

Abstract

Process for the preparation of a normally-tacky pressure-sensitive adhesive which comprises subjecting a solventless radiation-sensitive acrylate-containing polymerizable mass to radiation in the near UV region, at a rate of from about 0.1 to 7 milliwatts per square centimeter of the mass exposed.

Claims

1. A process for the preparation of a normally tacky pressure-sensitive adhesive comprising subjecting a suitable mass of a radiation-sensitized solventless liquid mixture containing as a major proportion thereof at least one acrylic acid ester of an alkyl alcohol, said alcohol containing from 4 to 14 carbon atoms, and at least one monomer copolymerizable therewith to radiation in the near ultraviolet region at a rate or irradiation in the 3000-4000 A wavelength range of not more than 7 milliwatts per square centimeter of the mass exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wavelengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range.

2. A process for the preparation of a normally tacky pressure-sensitive adhesive comprising subjecting a suitable mass of up to about 1.9 centimeters thickness of a radiation-sensitized solventless liquid mixture containing as a major proportion thereof at least one acrylic acid ester of an alkyl alcohol, said alcohol containing from 4 to 14 carbon atoms, and at least one monomer copolymerizable therewith to radiation in the near ultraviolet region at a rate of irradiation in the 3000-4000 A wavelength range of from 0.1 to 7 milliwatts per square centimeter of the mass exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wavelengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range, until at least about 95% of the monomer present in the mass has been polymerized, whereby a tacky, flexible pressure-sensitive adhesive having peel adhesion to glass greater than about 0.8 kilograms per centimeter and shear strength greater than 50 minutes is formed.

3. A process for the preparation of a normally tacky pressure-sensitive adhesive comprising the steps of

(1) preparing a suitably radiation-sensitized, solventless, liquid mixture comprising

(a) 70-98 parts of units of at least one alkyl acrylate of which the alkyl group contains from 4 to 14 carbon atoms and

(b) 2-30 parts of units of at least one modifying monomer copolymerizable therewith the sum of (a) and (b) amounting to 100 parts by weight, and

(c) 0.01-5 parts of a photoinitiator, and

(2) subjecting the mixture in a mass having a thickness of not more than about 1.9 cm. to radiation having wave lengths of 3000-4000 A at a rate of irradiation of from 0.1 to 7 milliwatts per square centimeter of the mass exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wave lengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range, until at least about 95% of the monomer has been polymerized,

whereby a tacky, flexible pressure-sensitive adhesive having peel adhesion to glass greater than about 0.8 kilograms per centimeter and shear strength greater than 50 minutes is formed.

4. A process according to claim 3 wherein the mixture contains 85-92 parts of (a) and 8-15 parts of (b), the sum of the two being 100 parts by weight.

5. A process according to claim 3 wherein the modifying monomer is acrylic acid.

6. A process for the manufacture of a pressure-sensitive adhesive tape comprising

(1) coating a flexible tape backing with up to about 125 micron layer of a viscous suitably radiation-sensitized solventless syrup containing at least one acrylic acid ester of an alkyl alcohol, said alcohol containing from 4 to 14 carbon atoms, and at least one monomer copolymerizable therewith,

(2) subjecting the layer to radiation in the near ultraviolet region at a rate of irradiation of 3000-4000 A wavelength of not more than 7 milliwatts per square centimeter of the layer exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wavelengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range.

7. A process for the manufacture of a pressure-sensitive adhesive tape comprising

(1) coating a flexible tape backing with up to about 125 micron layer of a viscous suitably radiation-sensitized solventless syrup containing at least one acrylic acid ester of an alkyl alcohol, said alcohol containing from 4 to 14 carbon atoms, and at least one monomer copolymerizable therewith,

(2) subjecting the layer to radiation in the near ultraviolet region at a rate of irradiation of 3000-4000 A wave length of from 0.1 to 7 milliwatts per square centimeter of the layer exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wave lengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range, until at least about 95% of the monomer has been polymerized,

whereby the syrup is converted to a tacky, flexible pressure-sensitive adhesive having peel adhesion to glass greater than about 0.8 kilograms per centimeter and shear strength greater than 50 minutes.

8. A process for the manufacture of a pressure-sensitive adhesive tape comprising

(1) coating a flexible tape backing with up to about a 125 micron layer of a prepolymerized syrup of a suitably radiation-sensitized solventless mixture comprising

(a) 70-98 parts of units of at least one alkyl acrylate of which the alkyl group contains from 4 to 14 carbon atoms and

(b) 2-30 parts of units of at least one modifying monomer copolymerizable therewith the sum of (a) and (b) amounting to 100 parts by weight, and

(c) 0.01-5 parts of a photoiniator, and

(2) subjecting the layer to radiation in the near ultraviolet region at a rate of irradiation of 3000-4000 A wave length of from 0.1 to 7 milliwatts per square centimeter of the layer exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wave lengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range, until at least about 95% of the monomer has been polymerized,

whereby the syrup is converted to a tacky, flexible pressure-sensitive adhesive having peel adhesion to glass greater than about 0.8 kilograms per centimeter and shear strength greater than 50 minutes.

9. A process according to claim 8 wherein the mixture contains 85-92 parts of (a) and 8-15 parts of (b), the sum of the two being 100 parts by weight.

10. A process according to claim 8 wherein the modifying monomer is acrylic acid.

11. A process for the preparation of a normally tacky pressure-sensitive adhesive comprising

(1) subjecting a suitable low viscosity liquid mixture of at least one acrylic acid ester of an alkyl alcohol, said alcohol containing from 4 to 14 carbon atoms and at least one monomer copolymerizable therewith to prepolymerizing conditions to form a relatively viscous syrup in which from about 5 to 10 percent of the monomers have been converted to polymer,

(2) forming a radiation-sensitive means of up to about 1.9 centimeters thickness comprising the syrup, and

(3) subjecting the mass to radiation in the near ultraviolet region at a rate of irradiation in the 3000-4000 A wavelength range of from 0.1 to 7 milliwatts per square centimeter of the mass exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wavelengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range, until at least about 95% of the monomer has been polymerized,

whereby a tacky, flexible pressure-sensitive adhesive having peel adhesion to glass greater than about 0.8 kilograms per centimeter and shear strength greater than 50 minutes is formed.

12. A process for the preparation of a normally tacky pressure-sensitive adhesive comprising

(1) subjecting a suitable low viscosity liquid mixture comprising

(a) 70-98 parts of at least one alkyl acrylate monomer of which the alkyl group contains from 4 to 14 carbon atoms and

(b) 2-30 parts of at least one modifying monomer copolymerizable therewith the sum of (a) and (b) amounting to 100 parts by weight,

to prepolymerizing conditions to form a relatively viscous syrup in which from about 5 to 10 percent of the monomers have been converted to polymer,

(2) forming a radiation-sensitive mass of up to about 1.9 centimeters thickness comprising the syrup, and

(3) subjecting the mass to radiation in the near ultraviolet region at a rate of irradiation in the 3000-4000 A wavelength range of from 0.1 to 7 milliwatts per square centimeter of the mass exposed, said radiation allowably also containing incidental radiation energy, the amount of said incidental radiation energy having wave lengths shorter than 3000 A being limited to not more than about 10% of the amount of energy in the 3000-4000 A range, until at least about 95% of the monomer has been polymerized,

whereby a tacky, flexible pressure-sensitive adhesive having peel adhesion to glass greater than about 0.8 kilograms per centimeter and shear strength greater than 50 minutes is formed.