WO1981000361A1

WO1981000361A1 - Lipo-surfactant coagulant for rubber

Info

Publication number: WO1981000361A1
Application number: PCT/US1980/000877
Authority: WO
Inventors: J Joung
Original assignee: American Hospital Supply Corp
Priority date: 1979-07-30
Filing date: 1980-07-14
Publication date: 1981-02-19
Also published as: BE884553A; EP0032505A4; EP0032505A1

Abstract

A coagulant for use in manufacture of latex rubber products, such as surgeon's gloves. The coagulant includes a lipo compound and a dispersing surfactant which provides easy mold release for the formed rubber products.

Description

Lipo-Surfactant Coagulant For Rubber

Technical Field

This invention relates to a coagulant for use in manufacture of latex rubber products, such as surgeon's gloves.

Background Art

It is well-known to use coagulants when dip orming latex rubber products. In forming a thin walled rubber product such as a surgeon's glove, condom, etc., a form is dip coated with a coagulant and then subsequently submerged into a latex dispersion. The coagulant causes the latex to gel up and form a film on the form. A typical coagulant is described in Patent 1,996,090.

One of the problems with coagulants is that they tend to cause the formed rubber part to stick to the mold. To overcome this, talc has been incorporated in coagulants. The talc, being of mineral origin, can withstand the high curing temperatures of approximately 260 F for the rubber product while on its form. However, the talc particles become dispersed throughout the formed rubber part and certain tale particles are at the surface of the product. This necessitates extensive washing in an effort to eliminate all loose talc particles in a product, such as a surgeon's glove that enters a surgical wound. It is undesirable to have any talc particles that may come loose during surgery. The medical literature has indicated that granuloma may be caused by talc or other particles that are not bio-absorbable. Efforts to eliminate talc from the coagulants results in a rubber product that cannot be stripped from the mold, and hence is useless. Also, attempts to substitute a silicone or mineral oil in the coagulant has caused wetting problems in dipping the glove form, as well as tending to have a plasticizing ef ect on the resultant rubber product. Latex, being a water dispersion, does not mix well with oil. Disclosure of Invention

The present invention overcomes the above problems with a coagulant that will both withstand the rubber curing temperatures of 260° F and also provide easy mold release of the cured rubber product. The coagulant is "talc free" and thus, the resultant cured glove is also talc free. To provide the mold release, a lipo compound, such as a lipid or lipophilic polymer and a nonionic surfactant is included in the coagulant. Such lipo compounds and surfactants are bio-compatible and are generally absorbable by the body.

Best Mode For Carrying Out The Invention

A lipo compound in a coagulant would not function properly for mold release because the lipo compound would separate from the coagu¬ lant. In the present invention, a nonionic surfactant is used to disperse the lipo compound. The lipo compounds can include lipids or lipophilic substances, such as fatty acids, fatty acid esters, fatty acid salts, • cholesterols, polyols, paraffin oils, mineral oils, vegetable oils, silicones, alkyl polyether alcohols and aryl polyether alcohols. Other lipophilic polymers could also be used as long as they were biologically compatible with the human body. The term "surfactant" is used in a broad meaning to include various surfactants, detergents, and dispersing agents, as well as ampho- teric surface active agents. Typical nonionic surfactants for use in the present invention include polysorbate, polyoxyethylene sorbitan, other polyethyleneoxy derivatives, fatty acid salts, alkyl-aryl sulfonates, alkyl sulfonates, alkyl sulfates, and silicone gylcols.

In preparing the coagulant solution, an aliquot of lipo compound is mixed with an equivalent of surfactant in aqueous solution, and then mixed with the remaining components of the coagulant. Sometimes heating is necessary to disperse the lipo compounds. The amount of surfactant should be enough to disperse the lipid into colloid or trans¬ lucent dissolution. Excessive amounts of surfactant will result in exces¬ sive loss of the lipo compound during extraction, as well as cause foaming. Too small an amount of surfactant will cause lipid droplets to float on the coagulant surfaces resulting in pin holes in gloves or other latex products. Depending upon the application, as well as the particular chemicals, the lipo compound and the surfactant each are present in the coagulant in a range of 0.2 to 3% by weight. Preferably, the lipo compound and surfactant are present in approximately equivalent amounts in the coagu¬ lant. Although the mechanism of the lipo compound and the surfactant is not totally understood, it is believed to cause mold release of the rubber product as follows:

1) The dispersed lipid and other nonvolatile components form a uniform film when the form is dipped and dried. 2) When the form is dipped into the latex, the film release coagulant forms latex coagulum, trapping the lipid dis¬ persion between the form and coagulum. 3) Upon extraction, the surfactant, being water soluble, can more readily diffuse out with other components of coagulant through the latex coagulum layer, whereas the lipo com¬ pound is more difficult to pass through the organophilic coagulum. Therefore, tiny lipo compound droplets are created between the form and coagulum. The lipo com¬ pound phase facilitates form release and everything attaches to the form surface of the glove or rubber product resulting in tack free surfaces and the form (which can be a ceramic glove form) becomes free of the lipo compound. Repeated dipping tests indicate the lipo compound need not be detergently cleansed from the form before the next glove is made.

It is very important to understand that any mold release agent in the coagulant must also withstand the curing heat of approximately

260 F and have minimal plasticizing effect on the cured rubber. The improved coagulant with the lipo compound and surfactant of the present invention meets this criteria.

Example 1

A coagulant was prepared according to the following formulation.

The coagulant contains 0.5% alkylaryl polyether alcohol (Triton X 100;

Rohm & Haas Co., 5000 Richmond, Philadelphia, Pennsylvania) dispersed by a polyethyleneoxy derivative (Emulphor On-877; GAF, 189 Wells

Avenue, Newton, Massachusetts).

O:*-:PI V/IFO Coagulant Formulation

Composition Weight %

Ca (NO₃)₂ 15

Zn (NO₃)₂ 10

Triton X 100 0.5

Emulphor ON-877 0.7

Water 18.8 Ethanol 65

The gloves were prepared using 30% solid content natural rubber latex and cured at 260° F for 30 minutes after extracting the coagulum for 5 minutes in running tap water. The gloves came off from the forms easily and the surface of the glove was not tacky.

Example 2 Poly dim ethylsiloxane (viscosity 100,000 C.P.) was dispersed into the coagulant as shown in the following table. When the coagulant was used to make a glove, excellent form release characteristics, as well as a slippery surface on the glove, resulted.

Coagulant Formulation

Composition Weight % , Ca (NO₃)₂ 20

Silicone Fluid 0.3

Emulphor ON-877 1.2

Ethyl Alcohol 25

Water 53.5

Example 3

Sorbitan Monooleate was incorporated into the coagulant by using a dispersing agent, polyoxyethylene sorbitan monooleate (Tween 80; ICI, Wilmington, Delaware). The resultant rubber glove surface felt like a leather surface. The formulation is shown in the following table. Coagulant Formulation

Composition Weight %

Ca (NO₃)₂ 10

Zn (NO₃)₂ 10

Sorbitan monooleate 1

Tween 80 1

Ethanol 60

Ethyl lactate 0.5

Water 17.5

Example 4

. Equal amounts of sorbitan stearate and Tween 80 were mixed together. In the mixture, water was added (4 fold by weight) and heated. The stearate dispersed vigorously upon heating by a burner and formed a colloidal suspension. In this case, the coagulant formulation was:

Composition Weight % Lipid suspension 3.5 Ca (NO₃)₂ 16 Zn (NO₃)₂ 10 Water 20 Alcohol 60 Ethyl lactate 0.5

OMPI IPO Example 5 One Kg of mineral oil was added into 4 Kg of Emulphor On-877 and homogenized by vigorous mixing. A mineral oil containing coagulant was prepared with it. In this case, the coagulant formulation was:

Composition Weight %

Ca (NO₃)₂ 15

Zn (NO₃)₂ 5

Water 15

Mineral oil suspension 2.5 Ethyl lactate 0.5

Ethyl alcohol ^• - ■ 62

In the above description, specific examples have been used to describe the invention. However, it is understood by those skilled in the art that certain modifications can be made to these examples without departing from the spirit and scope of the invention.

1^

OMPI .A

Claims

1. A coagulant for forming a rubber product, wherein the improve¬ ment comprises: a lipo compound in the coagulant; and a surfactant in the coagulant to disperse this lipo compound.

2. A coagulant as set forth in Claim 1, wherein the lipo compound and surfactant are each present in the coagulant in the range of 0.2 to 3% by weight.

3. A coagulant as set forth in Claim 1, wherein the lipo compound and surfactant are present in the coagulant in approximately equivalent amounts.

4. A mold releasing coagulant for forming a rubber product, wherein the improvement comprises: a lipo compound selected from the group consisting of lipids and lipophilic polymers in the coagulant; and a nonionic surfactant in the coagulant to disperse the lipo compound.

5. A coagulant as set forth in Claim 4, wherein the lipo compound is selected from the gorup consisting of fatty acids, fatty acid esters, fatty acid salts, cholesterols, polyols, paraffin oils, mineral oils, vegetable oils, silicones, alkyl polyether alcohols, and aryl polyether alcohols.

6. A coagulant as set forth in Claim 4, wherein the nonionic surfactant is selected from the group consisting of polysorbate, polyoxethylene sorbitan, polyethyleneoxy derivaties, fatty acid salts, alkyl-aryl sulfonates, alkyl sulfonates, alkyl sulfates, and silicone glycols.

7. A coagulant as set forth in Claim 4, wherein the surfactant is nonionic.

8. A coagulant as set forth in Claim 5, wherein the coagulant is capable of withstanding rubber curing temperatures.

9. A coagulant as set forth in Claim 8, wherein the rubber curing temperature is approximately 260° F.

10. A coagulant as set forth in Claim 4, wherein the coagulant is free of powders of mineral origin.

11. A coagulant as set forth in Claim 10, wherein the coagulant is free of talc

12. A coagulant as set forth in Claim 4, wherein the lipo compound and the surfactant are present in approximately equivalent amounts.

13. A mold releasing coagulant for forming a rubber product, wherein the improvement comprises: a lipo compound in the coagulant; a surfactant in the coagulant in an amount sufficient to disperse the lipo compound into a colloid dissolution.

14. A coagulant as set forth in Claim 13, wherein the colloid dissolution is translucent.

15. A coagulant as set forth in Claim 13, wherein the weight of the lipo compound and the surfactant in the coagulant are of approxi- mately equal weight percentages.