GB1575239A - Pile product and method of making the same - Google Patents

Description

(54) PILE PRODUCT AND METHOD OF MAKING THE SAME (71) We, BRUNSWICK CORPORATION, a corporation organized and existing under the laws of the State of Delaware, United States of America, of One Brunswick Plaza, Skokie, Illinois 60076, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to pile products and in particular to molded pile products, and to a method of making them.

As shown in our U.S. Patent 3,804,617, an improved synthetic resin pile product may be formed by a molding operation wherein the pile fibers extend from a base portion. The pile product may be so formed by means of a mold provided with a plurality of relatively small cross section, high aspect ratio (the ratio of the length to cross section) cavities. As indicated in the patent.

the pile product may be formed of suitable polymeric material, such as polyvinyl chloride, polyethylene, polypropylene, and poly urethane. Other patents relating to the molding of pile products include U.S. Patents 3,027,595, 3,141,051, 3,317,633, 3,316,592, 3,632,842 and 3,655,497.

One major problem with manufacturing molded pile products is to repeatedly remove the product from the mold without elongating or breaking the pile fibers. This problem becomes more acute as the pile fibers become longer and thinner. With known molding techniques it is believed impossible to repeatedly withdraw pile fibers from a mold where the aspect ratio (fiber length divided by fiber diameter) of the fiber is about 50 or greater.

We have now found that molded pile products in which the fiber aspect ratio is from 50 to 100 can be made without elongation or breakage of the fibers upon removal from the mold.

According to the present invention, there is provided a molded pile product comprising: (a) a base and a plurality of pile fibers extending upright from said base; (b) the fibers and base comprising at least 90 /O by weight of a copolymer of ethylene and vinyl acetate; (c) the fibers having an average diameter in the range of 4 to 10 mils, an average length in the range of 200 to 700 mils, an aspect ratio in the range of 50 to 100, and a fiber density in the range of 10 to 50%; and (d) the pile product having been molded by heat and pressure in cavities corresponding to the fibers of the pile product and removed from the cavities at a temperature 1400-1700F, the fibers exhibiting substantially no elongation or breakage in spite of removal from high aspect cavities at said elevated removal temperature.

The invention also provides a methbd of making such a product, which comprises: (a) heating to a temperature in the range 250 to 500"F a moldable mass comprising at least 90% by weight of a copolymer of ethylene and vinyl acetate; (b) subjecting the mass in a mold having cavities corresponding to the fibers of the pile product to a pressure in the range of 200 to 1200 p.s.i.; (c) cooling the mass in the mold; and (d) removing the molded pile product from the mold without substantial elongation or breakage of the fibers when the temperature of the product in the mold is in the range 140 to 1700F; wherein the mold cavities are such that the fibers have a diameter in the range of 4 to 10 mils, a height in the range of 0.2 to 0.7 inch, an aspect ratio in the range of 50 to 100, and a fiber.density in the range of 10 and 50%.

By fiber density we mean (the volume of fibers) divided by (fiber height times area of base-o pile product times 100).

The preferred fiber diameter is 5 to 6 mils, the preferred fiber length is 200 to 300 mils, the preferred aspect ratio is 50 to 60, and the preferred fiber density is 15 to 20%.

The pile fibers may be of equal length or some fibers may be longer than other fibers to provide a cut pile design. Moreover, the fibers may be of the same or different crosssectional shape. The preferred cross-sectional shape of the fibers is circular or oval; however, other shapes may be desired for aesthetic purposes. Similarly, the fibers may be tapered or untapered.

The EVA copolymer used to make a pile product of the invention gives the pile fibers a plush, soft, highly desirable feel. However, EVA copolymer is used in many applications as an adhesive. Therefore, one skilled in the art of making molded pile products would ordinarily not choose EVA copolymer because of the anticipated difficulties he would expect to encounter in removing the pile product from the mold. We have discovered, however, that by carefully controlling the molding conditions, the EVA copolymer can be molded into a plush pile product which is readily removed from the mold without breaking or elongating the pile fibers.

In the method of the invention, first a mass of polymeric material including at least 90 weight percent EVA copolymer is heated to a temperature in the range 250 to 500"F, preferably, from 275 to 300"F.

Next, this heated mass is subjected to a pressure in the range 200 to 1200 p.s.i., preferably 800 to 1000 p.s.i., to force the polymeric material into a mold having cavities corresponding to the fibers of the pile product. The mass of polymeric material in the mold is then cooled to a temperature in the range 140 to 1700F. When the molded pile product in the mold has cooled to this temperature, it is then removed from the mold. Care is taken to only apply the pressure for a period of time preferably not more than 130 seconds. Ordinarily, the time pressure must be applied to the mass of heated polymeric material ranges from 30 to 130 seconds. We have found that the mass of polymeric material should include a release agent, and preferably, the mold is also precoated with a release agent. Suitable release agents are fatty acids, and derivatives thereof such as fatty acid salts, fatty acid amides, or fatty acid esters, and compounds of silicon.

The EVA copolymer employed should preferably have a melt index in the range of 1 to 3, most preferably 2 to 3. Moreover, the EVA copolymer should preferably comprise 2 to 30 weight%, most preferably 2 to 8 weight %, of the vinyl acetate moiety.

Prior to molding, the release agent is blended with the EVA copolymer to form the molding composition. Approximately 1% by weight of release agent is generally used. In addition to the release agent, up to 10% - by weight or less of a filler material may be added to the polymeric material.

Such fillers may include, for example, pigments, carbon black, antioxidants and stabilizers.

We have found it desirable in order to improve the strength of the pile fibers to crosslink the molecules of the fibers after the pile product has been removed from the mold. This is accomplished most effectively by irradiating the pile product with an electron beam. Illustratively, the product may be irradiated with doses in the range of approximately 5 to 15 MR to effect such crosslinking when desired.

In order that the invention may be more fully understood, reference is made to the accompanying drawings, in which: FIGURE 1 is a schematic cross-section of one form of apparatus for carrying out one step in the molding of a pile product of the invention; FIGURE 2 is a horizontal cross-section taken substantially along the line 2-2 of Figure 1; FIGURE 3 is an isometric view of one embodiment of pile product of the invention; FIGURE 4 is a schematic view illustrating an irradiation step for effecting cross-linking of a pile product of the invention; and FIGURE 5 is a schematic illustration showing preheating of polymeric material.

In the exemplary embodiment of the invention as disclosed in the drawing, a pile product generally designated 10 is shown to comprise a base portion 11 and a plurality of fibers 12 upstanding from the base portion. The product is made from an ethylene vinyl acetate copolymer.

The EVA material may be introduced into the cavities 13 of a mold generally designated 14 to form the desired product 10. Thus, as shown in Figure 1, cavities 13 comprise elongated, relatively small crosssection cavities for molding a large number of fibers 12 so as to form a desired pile-type product 10. As best seen in Figure 2, one type of mold 14 may be formed of a plurality of plates 15 provided with small crosssection, outwardly opening recesses 16, which plates, when stacked, define a plurality of downwardly extending cavities 13. The plates may be secured in the stacked relationship by a suitable outer frame portion 17 defining an upper material receiving space 18.

The copolymer material, generally designated EVA, may be preheated such as by means of a conventional heater 19 with the material received in a suitable container 20; Alternatively, the material may be placed in the heated molding apparatus generally designated 21 including frame 17 and mold 14 with the mold being heated to the desired molding temperature, such as in the range of approximately 250 to 500"F.

A pressure plate 22 may be introduced into the recess 18 to apply a pressure to the heated EVA material in the range of approximately 200 to 1200 p.s.i. and for a preselected period of time up to approximately 130 seconds. A portion of the EVA material is thus caused to flow into the cavities 13 while the remaining portion of the material is retained above the mold 14, as shown by the dotted lines in Figure 1, thereby concurrently forming the base portion 11 and fiber portion 12 of the pile product.

As discussed above, the cavities may have a relatively high aspect ratio so that relatively fine fibers may be so formed of the selected EVA material while yet the formed fibers may be readily withdrawn from the cavities 13 upon a subsequent cooling of the molded product and lifting of the cooled product from the mold. As will be obvious to those skilled in the art, any suitable method of successively heating and cooling the mold may be utilized within the scope of the invention. One illustrative method, as shown, is to provide suitable passages 23 in a platen 24 juxtaposed to the molding apparatus 21 and selectively carrying heating and cooling fluids. Further illustratively, the pressure plate 22 may be provided with similar passages 25 to define a selective upper heating and cooling means.

The lifting of the formed pile product from the mold may be effected by injecting a compressed gas, such as nitrogen, through a suitable control valve 26 and a flow passage 27 to between the base portion 11 of the product and the upper surface 28 of the mold 14 subsequent to the cooling of the molded product to a desired lower temperature of approximately 140 to 1700F. The pressurized fluid may thusly further serve to cool the product during the removal thereof from the mold.

The molded product may be further irradiated, as shown in Figure 4, by a conventional electron irradiation apparatus generally designated 29 to effect crosslinking of the EVA material when desired. Illustratively, the pile product may be irradiated with dosages of approximately 5 to 15 MR whereby the melt characteristics of the EVA material are substantially improved from a normal melt point of approximately 220 225 to 3500F. and by suitably irradiating the EVA material, the material may be completely cured to prevent any melting thereof tip to the char point.

As further discussed above, a small percentage of mold release agent may be included in the EVA copolymer. The release agent is preferably provided in an amount less than 1 % by weight of the mold material, and as indicated above, preferably comprises a fatty acid material, one example being the fatty acid amide material marketed under the trade name Kemamide by Kraftco Corporation of Memphis, Tennessee.

For further improved release of the fibers from the mold cavities, it is desirable to provide an external release agent on the mold cavity surface, one example thereof being a silicone fluid dissolved in perchloroethylene.

It has been found that by controlling the molding temperature, the use of release agents and other parameters, as discussed above, a pile product is obtained effectively avoiding undesirable elongation or breaking of the fibers during the removal thereof from the mold and providing improved pile product characteristics in the final product.

A typical example of the formation of the desired product is one wherein the EVA copolymer was molded at a molding temperature in the range of 275 to 340"F. at a compression pressure in the range of approximately 1000 to 1200 p.s.i. for approximately one minute with the release cool temperature approximately 175 F. It has been found that the application of the pressure plate as a cooling plate provides an improved rapid forming of the pile product.

As will be obvious to those skilled in the art, the molding operation could be formed in a heating press with the mold and molded product being transferred to a cooling press for effecting the sequential steps, if so desired.

The disclosed method of forming the EVA pile product may be utilized in connection with continuous molding operations where the mold may be successively heated and cooled as in a rotary mold device.

The resultant EVA pile product 10 exhibits high resilience, high abrasion resistance, high soil resistance, and low static electricity propensity. At present, the cost of the EVA copolymer material is approximately one-half that of conventional polyvinyl chloride materials. Further, it has been found that whereas pile fabrics formed of polyvinyl chloride fabric have an objectionable wet hand, the EVA pile product made in conformity with the present invention has a desirable dry hand feel.

As the EVA material is capable of ready pigmentation, the product may be formed in a wide range of colors which may be effectively fadeproof in contradistinction to the conventional dye colors used in conventional carpeting, thereby providing a further highly desirable advantage over the prior art materials. As the cavities 13 and resultant fibers 12 have a very small cross section, the fibers do not resist the person's foot when the product is used as a carpet so as to avoid giving the walker a feeling of reactive thrust Thus, in view of the improved abrasion resistance, soil resistance, resistance to static charge buildup, and stain resistance, the pile product comprises an excellent candidate for carpeting material.

The use of EVA copolymer in such pile products, as briefly indicated above, is contraindicated in view of the use of EVA copolymers extensively as hot melt adhesives inasmuch as the molding material must not adhere to the surfaces of the mold cavities while yet the fibers must have high aspect ratios making the satisfactory use of an adhesive material for this purpose unexpected.

WHAT WE CLAIM IS:- 1. A molded pile product comprising: (a) a base and a plurality of pile fibers extending upright from said base; (b) the fibers and base comprising at least 90% by weight of a copolymer of ethylene and vinyl acetate; (c) the fibers having an average diameter in the range of 4 to 10 mils, an average length in the range of 200 to 700 mils, an aspect ratio in the range of 50 to 100, and a fiber density in the range of 10 to 50%; and (d) the pile product having been molded by heat and pressure in cavities corresponding to the fibers of the pile product and removed from the cavities at a temperature 1400-170F, the fibers exhibiting substantially no elongation or breakage in spite of removal from high aspect cavities at said elevated removal temperature.

2. A pile product according to claim 1, wherein said copolymer of ethylene and vinyl acetate including 2 to 30% by weight vinyl acetate.

3. A pile product according to claim 2, wherein said copolymer of ethylene and vinyl acetate includes 2 to 8% by weight vinyl acetate.

4. A pile product according to claim l, 2 or 3, wherein the fibers and base are molded from a mixture comprising the said copolymer and a mold release agent which is a fatty acid or derivative thereof, and wherein the copolymer has a melt index of from 1 to 3.

5. A pile product according to claim 1-, 2, 3 or 4, wherein the fibers further include up to 10% by weight of filler material.

6. A pile product according to any one of claims 1 to 5, wherein the fiber density is 18 to 20% and the fibers have an average diameter of 4 to 6 mils.

7. A pile produce according to any of claims 1 to 6, wherein the fibers include a pigment to provide colour.

8. A pile product according to any of claims 1 to 7, wherein the fibers have a sequentially molded and electron-irradiated microstructure.

9. A pile product according to claim 8, wherein the microstructure comprises a crosslinked structure of said copolymer.

10. A pile product according to claim 8, wherein the microstructure is pre-selected to prevent melting of the fibers at temperatures up to approximately 350"F.

11. A pile product substantially as herein described with reference to Figure 3 of the accompanying drawings.

12. A method of making a molded pile product as claimed in claim 1, which comprises: (a) heating to a temperature in the range 250 to 500OF a moldable mass comprising at least 90% by weight of a copolymer of ethylene and vinyl acetate; (b) subjecting the mass in a mold having cavities corresponding to the fibers of the pile product to a pressure in the range of 200 to 1200 p.s.i.; (c) cooling the mass in the mold; and (d) removing the molded pile product from the mold without substantial elongation or breakage of the fibers when the temperature of the product in the mold is in the range 140 to 1700F; wherein the mold cavities are such that the fibers have a diameter in the range of 4 to 10 mils, a height in the range of 0.2 to 0.7 inch, an aspect ratio in the range of 50 to 100, and a fiber density in the range of 10 and 50%.

13. A method according to claim 12 wherein the copolymer includes from 2 to 30% by weight vinyl acetate.

14. A method according to claim 13 wherein the copolymer includes from 2 to 8% by weight vinyl acetate.

15. A method according to claim 12, 13 or 14 wherein said mass includes filler material in an amount of up to 10% by weight.

16. A method according to claim 12, 13, 14 or 15, wherein the mass includes a release agent, and wherein said mold is coated with a release agent.

17. A method according to any of claims -12 to 16, wherein said pressure is provided for a period of less than 130 seconds.

18. A method according to any of claims 12 to 17, further including the step of treating the molded product to effect cross-linking of the copolymer.

19. A method according to claim 18 wherein the cross-linking is effected by electron irradiation of the molded product.

20. A method according to any of claims 12 to 19, wherein after the molded. product has been formed in the mold, pressurized fluid is introduced between said base and said mold for further cooling the product.

21. A method of making a pile product

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (22)

**WARNING** start of CLMS field may overlap end of DESC **. to avoid giving the walker a feeling of reactive thrust Thus, in view of the improved abrasion resistance, soil resistance, resistance to static charge buildup, and stain resistance, the pile product comprises an excellent candidate for carpeting material. The use of EVA copolymer in such pile products, as briefly indicated above, is contraindicated in view of the use of EVA copolymers extensively as hot melt adhesives inasmuch as the molding material must not adhere to the surfaces of the mold cavities while yet the fibers must have high aspect ratios making the satisfactory use of an adhesive material for this purpose unexpected. WHAT WE CLAIM IS:-

1. A molded pile product comprising: (a) a base and a plurality of pile fibers extending upright from said base; (b) the fibers and base comprising at least 90% by weight of a copolymer of ethylene and vinyl acetate; (c) the fibers having an average diameter in the range of 4 to 10 mils, an average length in the range of 200 to 700 mils, an aspect ratio in the range of 50 to 100, and a fiber density in the range of 10 to 50%; and (d) the pile product having been molded by heat and pressure in cavities corresponding to the fibers of the pile product and removed from the cavities at a temperature 1400-170F, the fibers exhibiting substantially no elongation or breakage in spite of removal from high aspect cavities at said elevated removal temperature.

2. A pile product according to claim 1, wherein said copolymer of ethylene and vinyl acetate including 2 to 30% by weight vinyl acetate.

3. A pile product according to claim 2, wherein said copolymer of ethylene and vinyl acetate includes 2 to 8% by weight vinyl acetate.

4. A pile product according to claim l, 2 or 3, wherein the fibers and base are molded from a mixture comprising the said copolymer and a mold release agent which is a fatty acid or derivative thereof, and wherein the copolymer has a melt index of from 1 to 3.

5. A pile product according to claim 1-, 2, 3 or 4, wherein the fibers further include up to 10% by weight of filler material.

6. A pile product according to any one of claims 1 to 5, wherein the fiber density is 18 to 20% and the fibers have an average diameter of 4 to 6 mils.

7. A pile produce according to any of claims 1 to 6, wherein the fibers include a pigment to provide colour.

8. A pile product according to any of claims 1 to 7, wherein the fibers have a sequentially molded and electron-irradiated microstructure.

9. A pile product according to claim 8, wherein the microstructure comprises a crosslinked structure of said copolymer.

10. A pile product according to claim 8, wherein the microstructure is pre-selected to prevent melting of the fibers at temperatures up to approximately 350"F.

11. A pile product substantially as herein described with reference to Figure 3 of the accompanying drawings.

12. A method of making a molded pile product as claimed in claim 1, which comprises: (a) heating to a temperature in the range 250 to 500OF a moldable mass comprising at least 90% by weight of a copolymer of ethylene and vinyl acetate; (b) subjecting the mass in a mold having cavities corresponding to the fibers of the pile product to a pressure in the range of 200 to 1200 p.s.i.; (c) cooling the mass in the mold; and (d) removing the molded pile product from the mold without substantial elongation or breakage of the fibers when the temperature of the product in the mold is in the range 140 to 1700F; wherein the mold cavities are such that the fibers have a diameter in the range of 4 to 10 mils, a height in the range of 0.2 to 0.7 inch, an aspect ratio in the range of 50 to 100, and a fiber density in the range of 10 and 50%.

13. A method according to claim 12 wherein the copolymer includes from 2 to 30% by weight vinyl acetate.

14. A method according to claim 13 wherein the copolymer includes from 2 to 8% by weight vinyl acetate.

15. A method according to claim 12, 13 or 14 wherein said mass includes filler material in an amount of up to 10% by weight.

16. A method according to claim 12, 13, 14 or 15, wherein the mass includes a release agent, and wherein said mold is coated with a release agent.

17. A method according to any of claims -12 to 16, wherein said pressure is provided for a period of less than 130 seconds.

18. A method according to any of claims 12 to 17, further including the step of treating the molded product to effect cross-linking of the copolymer.

19. A method according to claim 18 wherein the cross-linking is effected by electron irradiation of the molded product.

20. A method according to any of claims 12 to 19, wherein after the molded. product has been formed in the mold, pressurized fluid is introduced between said base and said mold for further cooling the product.

21. A method of making a pile product

as claimed in claim 1 substantially as herein described with reference to the accompanying drawings.

22. A molded pile product as claimed in claim 1 when made by the method of any of claims 12 to 21.