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Solventless compounding and coating of non-thermoplastic hydrocarbon elastomers

a technology of non-thermoplastic hydrocarbon elastomers and solvent-free compounding, which is applied in the direction of adhesive processes using foamed adhesives, adhesive types, film/foam adhesives, etc., can solve the problem that no oxygen-available gas is intentionally injected into the compounding device, and achieves the problem of elastomer crosslinking during processing, short time period, and reduced molecular weight of elastomer reduction

Inactive Publication Date: 2000-09-05
3M INNOVATIVE PROPERTIES CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention comprises a process for the solvent free compounding of non-thermosettable PSAs based upon a tackified non-thermoplastic hydrocarbon elastomer. The process employs a continuous compounding device and hot melt processing techniques. The adhesive composition can be compounded without separate batch pre-mastication of the elastomer and without the use of significant amounts of plasticizing aids to reduce the viscosity of the composition to render it processable. Additionally, the adhesive composition can be applied to a moving web directly from the compounding device so as to provide a continuous method for the manufacture of a PSA tape.
Aerobic processing may be advantageously utilized when the hydrocarbon elastomer will preferentially undergo chain scission rather than crosslinking and / or chain extension. Aerobic processing allows a greater reduction in the molecular weight of the elastomer in a relatively short period of time. Additionally, aerobic processing allows manufacture at lower temperatures. As a result, thermally sensitive materials may be compounded with the hydrocarbon elastomer in the process of the invention.
Anaerobic processing may be advantageously utilized when elastomers which crosslink under oxidative conditions were used. This mitigates the problem of these elastomers crosslinking during processing. Anaerobic processing may also be used with elastomers that do not crosslink under oxidative conditions so as to achieve a higher molecular weight than would be achieved under aerobic conditions. This increases the cohesive strength of the adhesive and minimizes the degree of later crosslinking needed to provide enhanced cohesive strength. Anaerobic processing of either type of elastomer also results in adhesives having lower odor and lighter color.

Problems solved by technology

Anaerobic processing means that no oxygen-available gas is intentionally injected into the compounding device.

Method used

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  • Solventless compounding and coating of non-thermoplastic hydrocarbon elastomers
  • Solventless compounding and coating of non-thermoplastic hydrocarbon elastomers
  • Solventless compounding and coating of non-thermoplastic hydrocarbon elastomers

Examples

Experimental program
Comparison scheme
Effect test

example 1

Natsyn.TM. 2210 synthetic polyisoprene (available from Goodyear Tire and Rubber Co.) was pelletized using a Moriyama pelletizer and dusted with talc. This material was then fed to .[.Zone.]. .Iadd.Section .Iaddend.1 of the .[.twin screw.]. .Iadd.screw, shown in FIG. 3 which was installed in the .Iaddend.extruder 20 .Iadd.of FIG. 1, .Iaddend.at a rate of 68.0 g / min using a K-Tron loss-in-weight feeder which continuously monitored the weight of the material in the hopper. The elastomer and talc were transported from .[.Zone.]. .Iadd.Section .Iaddend.1 to .[.Zone.]. .Iadd.Section .Iaddend.2 .[.by.]. .Iadd.of .Iaddend.the screw and was masticated in .[.Zone.]. .Iadd.Section .Iaddend.2. The elastomer was transported through .[.zones.]. .Iadd.Section .Iaddend.3 .[.and.]. .Iadd.to Section .Iaddend.4 where additional mastication occurred, to .[.zone.]. .Iadd.Section .Iaddend.5 where a sample of the elastomer was removed and found to have an inherent viscosity (IV) of 2.68 dl / g in toluene me...

example 2

Example 1 was repeated except that after being coated onto the creped paper backing, the backing continued to move at 30 ft / min (9.1 m / min) and the adhesive layer was exposed in line to electron beam radiation at a dose of 6 MRads. The irradiated PSA masking tape had improved cohesive strength.

example 3

The equipment and conditions employed in Examples 1 were repeated in Example 3 with the following exceptions. Smoked sheet natural rubber

(available from The Ore and Chemical Company, Inc.) was ground to particles approximately one quarter inch (0.63 cm) in diameter and dusted with talc. The rubber particles were fed to .[.Zone.]. .Iadd.Section .Iaddend.1 of the .[.twin screw.]. .Iadd.screw, shown in FIG. 3 which was installed in the .Iaddend.extruder 20 .Iadd.of FIG. 1.Iaddend., at a rate of 68.0 g / min. The elastomer and talc were transported from .[.Zone.]. .Iadd.Section .Iaddend.1 to .[.Zone.]. .Iadd.Section .Iaddend.2. The elastomer was masticated there and was then transported through .[.zones.]. .Iadd.Section .Iaddend.3 .[.and.]. .Iadd.to Section .Iaddend.4, where additional mastication occurred, to .[.zone.]. .Iadd.Section .Iaddend.5 where a sample of the elastomer was removed and found to have an inherent viscosity of 4.7 dl / g in toluene measured at a concentration of 0.15 g / ...

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Abstract

A solvent-free hot melt process, for preparing a non-thermosettable, pressure-sensitive adhesive from a tackified non-thermoplastic hydrocarbon elastomer. The process employs a continuous compounding device that has a sequence of alternating conveying and processing zones. The processing zones masticate and mix materials in them. Non-thermoplastic elastomers having high molecular weight may be readily compounded into adhesives in the process.

Description

FIELD OF THE INVENTIONThis invention relates to a solvent free, hot melt process for the manufacture of a non-thermosettable, pressure sensitive adhesive (PSA) from a tackified, non-thermoplastic hydrocarbon elastomer.BACKGROUND OF THE INVENTIONPressure sensitive adhesives based on non-thermoplastic hydrocarbon elastomers such as natural rubber, butyl rubber, synthetic polyisoprene, ethylene-propylene, polybutadiene, polyisobutylene, or styrene-butadiene random copolymer rubber, are well known in the art. The dominant means of processing such adhesives comprises masticating the elastomer on a two roll mill or in a Banbury type internal mixer, dissolving the elastomer and other adhesive components in a hydrocarbon solvent, coating the solution onto a backing, and drying the coated product to remove the solvent. This technology is discussed in Handbook of Pressure Sensitive Adhesive Technology, D. Satas (ed.), p. 268. Van Nostrand, N.Y., (1989). The solvent process has the disadvantag...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): B29C47/02B29C47/06B29C47/50B29C47/10B29C47/38C09J5/08C09J7/02B29C47/40B29C71/02C08L21/00B29C48/08B29C48/15B29C48/21B29C48/29B29C48/38B29C48/40B29C48/405
CPCB29C47/0047B29C47/02B29C47/065B29C47/1063B29C47/1081B29C47/50C09J5/08C09J7/0214B29C47/0021B29C47/367B29C47/40B29C71/02B29K2023/22B29K2105/0005B29K2105/24C08L21/00C09J2421/00C09J7/383B29C48/15B29C48/297B29C48/29B29C48/08B29C48/0014B29C48/21B29C48/387B29C48/38B29C48/405B29C48/40
Inventor BREDAHL, TIMOTHY D.LEVERTY, HAROLD W.SMITH, ROBERT L.BENNETT, RICHARD E.YARUSSO, DAVID J.MUNSON, DANIEL C.COX, GEORGE E.
Owner 3M INNOVATIVE PROPERTIES CO
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