WO1997027242A1

WO1997027242A1 - Method for reclaiming fused vinyl plastisols

Info

Publication number: WO1997027242A1
Application number: PCT/US1997/000919
Authority: WO
Inventors: C. Edward Terry; Connie D. Hensler
Original assignee: Interface, Inc.
Priority date: 1996-01-23
Filing date: 1997-01-22
Publication date: 1997-07-31
Also published as: EP0876425A4; AU1751797A; NZ331450A; BR9707171A; IL125302A0; EP0876425A1; NO983374D0; HUP9901859A2; HUP9901859A3; NO983374L; PL327992A1; TR199801404T2; AU715814B2; CN1214061A; JP2000504367A

Abstract

A method is disclosed for recycling fused vinyl plastisols. The vinyl plastisols are comminuted and dissolved in a solvent, such as cyclohexanone, dichloromethane, hexane, chloroform, methyl ethyl ketone or ethyl acetate. A plasticizer is added to the solvent mixture after the vinyl plastisol has dissolved, and the solvent is removed from the mixture under vacuum.

Description

METHOD FOR RECLAIMING FUSED VINYL PLASTISOLS

Field of the Invention

The present invention pertains generally to the field

of recycling polymeric materials. More particularly, the

invention is a method for reclaiming fused vinyl plastisols,

such as polyvinyl chloride that is used as a backing

material for carpets.

Background of the Invention

Vinyl plastisols are solid or foamed plastics that

typically comprise, for example, polyvinyl chloride,

phthalate plasticizers, inert fillers and miscellaneous

pigments and processing aids. One of the most common uses

of such materials is as a backing material for residential

and commercial carpet products.

One concern associated with such products is the

problem of recycling them when their useful product life has

ended. This is particularly true for carpet products, given

the huge amounts of carpet that are disposed of each year,

and the large amounts of vinyl plastisols that are

incorporated into such products. In addition, large amounts of backing material are collected as scraps during the

carpet manufacturing process.

Heretofore, the primary method for recycling the

backing component of carpets has been to grind the vinyl

plastisol backing material into small pieces, which are

thermoformed into plastic parts. Cryogenic grinding has

also been used, in which the vinyl plastisol is first

chopped into relatively small pieces, then frozen, then

ground into a powdery form while frozen. This powder can

then be blended in with new plastisol to form new backing

layer. However, such approaches tend to be very labor

intensive, as a result of the mechanical grinding

operations. Cryogenic methods also have the added

disadvantage of the required energy costs associated with

freezing the material . Accordingly, it would be useful to

have a method for recycling such materials that does not

depend on purely mechanical operations such as grinding or

chopping. The present invention provides such a method.

Summary of the Invention

In a basic aspect, the present invention is a method

for recycling fused vinyl plastisols using chemical, rather than purely mechanical means. The invention allows such

materials to be returned to their original liquid state,

allowing them to be re-used to form new products by casting

them as a film or mold and fusing the materials back into a

solid or foamed vinyl part in any of a variety of known

manners. In the case of vinyl plastisol backings for

carpets, the discarded or scrap materials can be returned to

their original liquid state and re-used to form new carpet

backing.

The method generally comprises the steps of 1)

comminuting the fused vinyl plastisol, preferably by

grinding or chopping the material, to form particles of

reduced size; 2) adding to the particles one or more

solvents selected from the group consisting of

cyclohexanone, dichloromethane, hexane, chloroform, methyl

ethyl ketone and ethyl acetate, to solvate the particles; 3)

adding additional plasticizer that is compatible with the

original plasticizers used in the vinyl; and 4) removing the

solvent from the mixture, preferably by drawing the solvent off under vacuum. Detailed Description of Preferred Embodiment In a preferred embodiment, the vinyl plastisol to be

reclaimed is ground or cut to approximately .25 inches in

diameter pieces for ease of handling and to speed the

reclamation process by increasing surface area of the

material. Any of a variety of commercial machines can be used for this purpose, with such methods being well known to

persons of ordinary skill in the art.

This ground vinyl is then added to a bath of solvent. The solvent may include one or a combination of the

following: cyclohexanone, dichloromethane, hexane,

chloroform, methyl ethyl ketone, ethyl acetate. Heat and/or

agitation may be applied to the solvent/plastisol mixture to speed the solvation process.

After complete solvation of the vinyl, additional

plasticizer that is compatible with the original plasticizers used in the vinyl are added to the mixture.

These may include: phthalate esters, adipates, azelates,

trimellitates, benzoates, and polymeric plasticizers.

Under a vacuum, the solvent is drawn off and the remaining mixture is strained to remove any unwanted components. The solvent is preferably reclaimed for reuse

in the process, using known techniques.

The remaining mixture is a highly plasticized material.

In the case of a polyvinyl chloride material, a dispersion

grade polyvinyl chloride is added to the reclaimed material

to achieve a castable vinyl plastisol. In this form it can

then be used in a standard plastisol application.

A particularly preferred embodiment of the process is

described below, using flexible PVC carpet backing material

as the material to be reclaimed. In the first step,

flexible PVC is ground or chopped to coarse particle size.

The size of the particles will determine the length of the

solvating step.

The chopped vinyl scrap is blended with solvent, such

as dichloromethane, with approximately one part vinyl added

to four parts solvent. This solvent/scrap mixture is aged

for a period of about 24 hours and agitated intermittently

to increase the speed of solvation. Persons of skill in the

art will recognize that the period of solvation may vary,

depending on the nature of the plastisol and solvent, the

temperature, and other factors. Once all the vinyl has been solvated, approximately 6

parts of DINP (diisononylphthalate) is added as a

plasticizer. This mixture of solvent, vinyl, and DINP is

transferred to a rotary vacuum dryer. Using a closed

system, the solvent is removed from the mixture and captured

in a separate container.

The remaining slurry is a plastisol that is highly plasticized. Resin, filler, and stabilizers can be added to

this mixture in the rotary vacuum dryer, or in a rotary

mixer. The resulting product can be used to make new backing

material (or other products) in a normal manner.

While in the foregoing there have been described

various preferred embodiments of the present invention, it should be understood that the invention is not limited to

those embodiments and that various modifications may be made

to those embodiments without departing from the scope and

spirit of the invention as claimed below.

Claims

What is claimed is:

1. A method for reclaiming a fused vinyl plastisol

material comprising the steps of a) comminuting the

plastisol material to form particles of reduced size; b)

adding to the particles a solvent selected from the group

consisting of cyclohexanone, dichloromethane, hexane,

chloroform, methyl ethyl ketone and ethyl acetate, to form a

mixture of solvent and particles; c) dissolving the

particles in the mixture; d) adding a plasticizer to the

mixture; and e) removing the solvent from the mixture.

2. The method of claim 1 wherein the solvent is removed

from the mixture by pulling a vacuum on the mixture.

3. The method of claim 1 wherein the vinyl plastisol is

polyvinyl chloride.