CA1060638A - Molded pile product and method making such a product - Google Patents

Abstract

Abstract of the Disclosure A pile product comprising a plurality of relatively long, thin face fibers extending from a base is molded from a crosslinkable polymeric material. During formation of the fibers, crosslinking of the polymeric material is initiated by heat activating a substance incorporated in the polymeric material which promotes crosslinking. Crosslinking imparts hot strength to the pile fibers so that the pile product, while still hot, can be removed from the mold without materially deforming the fibers. Consequently, the time it takes to mold the pile product is significantly reduced, thereby increasing productivity and lowering the cost of the product. Moreover energy is conserved because the mold is not continuously cycled between high And low extremes in temperature.

Description

o60638 : ~
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. . . Background ~- .
For many years pile products have been used, for example, in outer garments, shoes, carpets and wall coverings.
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In ~he carpet industry, conventional commercial processes for manufacturing such pile products call for tufting yarns through a suitable backing material such as woven poly-propylene or jute yarns. One way to simplify the manufacture of pile products is to mold such products directly from thermo-plastics. In such molding processes, a thermoplastic polymer is heated to its softening point and forced into a mold having cavities corresponding to the pile fibers. Examples of typical prior art molding processes are described in U. S. Patent Nos.
3,027,595; 3,141,051; 3,317,644; 3,517,094; 3,632,8~2;
3,533,895; and 3,804,617.
In general, known molding pxocesses required that -~the mold be cooled after the formation of the pile products ~so that the polymer solidifies sufficiently to permit the pile product to be removed from the mold. Such molding pro-cesses are acceptable provided the fibers have a configuration which lends itself to easy removal from the mold. Short, - relatively thick fibers can be xeadily removed from the mold, but as the fiber length increases and the fiber diameter de-~ creases, it becomes more difficult to remove such long thin fibers from the mold without severely damaging or defoxming the fibers. Frequently, such long, thin fibers are pulled from the~backing during removal from the mold to produce bare patches in the plle material, or they yield and stretch to ~ -produce areas whexe the pile fibers are severely elongated.

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lhe Invention We have now discovered a novel method for making molded pile products and employ this method to make a novel molded pile product. The central feature of our method is employing a crosslinkable polymeric material to make pile products and initiating crosslinking of the polymeric material during the formation of thé pile fibers. Any resinous material that may be molded and crossslinlced would be a suit-able polymeric material Polymers, copolymers or mixtures thereof may be used. Generally, suitable polymers and co- ;
polymers would have a molecular weight of about 500 or greater.
and be formed by addition or condensation polymerization re-actions. Crosslinking of such polymeric materials would en-tail the formation of a chemical bond between macromolecules through, for example, addition, substitution, condensation, .::
or rearrangement reactions. Initiator systems for.promoting such crosslinking may involve free radical sources, ionic ;~
species, or abstraction of molecular components from the macro-molecules. Suitable techniques to achieve crosslinking are disclosed in U. S. Patent Nos. 2,826,570; 2,849,028; ~.

2,919,474; 3,036,981; and 3,242,159. ~ :
In our method, the polymeric.material preferably ~ ~
is first compressed into a thin sheet or preform incorporating ~: -a heat responsive substance which,.upon being heated, promotes .
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crosslinking of individual molecules of the polymeric material. The preform is placed in a hot mold including a plurality of cavities corresponding to the pile fibers.
The surface of the preform in contact with the hot mold immediately begins to soften and the heat initiates cross-linking of the polymeric material. Simultaneously, the preform is subjected to a uniform pressure to force the softened polymeric material into the cavities of the mold.
Because of crosslinking, the molten polymeric material in the cavities gradually transforms into a gel and then into a solid which has hot strength. This transformation occurs without a significant drop in the temperature of the mold, (normally, mold temperature drops only about 5 - 10C).

Molding Composition The most preferred molding composition used to make the molded pile product of our invention includes the following proportions of ingredients:
Weight Percent~
Polymeric material 10 - 99 20~; Crosslinking promoters0.5 - 5 Monomers 0 - 70 Additives 0 - 70 :.P' _~_ .

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106iO63~3 ~ olymeric Material: ~ wide variety of starting polymeric materials may be used provided that they are crosslinkable. The preferred physical and chemical properties of such startin~ polymeric materials are as follows:

PROPERTY PREFERRED RANGE
Softening Point (C) 40 - 180 Melt Index (grams/
10 min.~ .5 - 100 Specific gravity 0.9 - 1.5 Genexally, suitable starting polymeric materials are polymers, copolymers or mixtures thereof derived from polymerizable organic compounds such as olefin hydrocarbons, vinyl compounds, diene compounds, esters, and urethanes.
Examples of suitable oleinic polymeric materials are poly-mers and copolymers of ethylene, propylene, methylpentene and/or butylene. Examples of suitable vinyl polymeric materials are polymers and copolymers o vinyl acetate, vinyl chloride, styrene, ethylacrylate, diethylfumarate methylmethacrylate and/or butylacrylate. Examples of suit-able diene polymeric materials are polymers and copolymers of butadiene, isoprene, and chloroprene. Examples of suitable ester type polymeric materials are the polymers and copolymers of glycol or glycolether phthalates, maleates, fumarates, itaconates, succinates, adipates and/or sebacates~ Examples of suitable urethane polymeric materials are polymers made by the reaction of aliphatic and aromatic diisocyanates with polyhydric esters and ethers. ~he olefinic polymers and co-polymers may be halogenated or halogen sulfonated to improve their resistance to solven~s and burning.
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1061)638 Ethylene vinyl acetate copolymer is the major component of the most preferred polymeric material~ Usually the preferred polymeric material will contain from about 15 to about 99 weight percent ethylene ~inyl acetate copolymer.
The percent vinyl acetate of such copolymer normally ranges between 5 to 45 percent. Typically, the most preferred ethylene vinyl acetate copolymer has a vinyl acetate content of 33 percent, a melt index of 25, a tensile strength of 98,4 kilograms/cm2 (1400 p.s.i.~, a percentage elongation of 900, and a stiffness of 70.3 kilograms/cm2 (lO00 p.s.i.), and a Shore hardness of A65.
Crosslinking Promoters: Examples of substances which promote crosslinking are (a) peroxide compounds, with or with- ~ -out added accelerators, (b) mixtures of peroxide compounds, silicon compounds and suitable catalysts, (c) azo compounds, or (d) a mixture of zinc oxide and sulfur. Many of the above substances generated free radicals which promote crosslinking;
however, substances which promote crosslinking by addition or condensation~reactions could also be used. The above cross-linking promoters may also be blended with monomers and then mixed w1th polymeric materiaL prior to molding.
;~ , The preferred substances used to promote crosslinking . ~
are the peroxide and azo compounds. The,peroxides may be blended with the polymeric material prior to molding, or mixed with monomers and then incorporated into the polymeri~ material ~`~ prior to molding. When the peroxides or azo compounds are , ~ .

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klended with the polymeric material, the temperature is controlled so that, during blending, it is below the temperature at which decomposition of the promoter is significant.
The preferred peroxide compounds are benzoyl peroxide, dicumyl peroxide,2.5 bis(tertiary butYl PeroXY)2, 5 dimethyl hexane, ~ bis(tertiary butvl ~eroxy) diisopropylbenzene di(tertiary)butyl-diperphthalate, and tertiary butyl perbenzoate. The preferred accelerators are cobalt naphthenate, lead naphthenate, dimethYl aniline.

The preferred silicon compounds are vinyl tri-ethoxy silane and vinyl trimethoxy silane. The preferred catalyst to be used with the silicon compounds is dibutyl tin dilaurate.
The preferred azo compounds are azo bis diisobutyro-nitrile, and 2 tertiary butyl azo dimethoxy - 4 - methyl pentane.
Monomers: Polymerizable monomers may be used in con3unction with peroxide compounds and polymeric materials.
Such monomer will polymerize during formation of the fibers and promote crosslinking. The preferred monomers are:
trimethylol propane trimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylates, triallyl cyanurate, triallyl phosphate~and diallylphtalate.
_~ 25 Additives: Preferably the starting polymeric mateFial is mixed with fillers such as silica, carbon black, , . . .
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~0610638 talc, clay, etc., to improve proper~ies and reduce cost.
~ntioxidants, dyes and pigments, ultra-violet absorbers and stabilizers, anti-fungal and anti-bacterial agents, and mold release agents may also be added.

Characteristics of Pile Product and Method of Making Such Product Broadly, ~he pile product can be viewed as a base having a given surface area with protuberances extending from the surface of the base. These protuberances have a total surface area which is se~eral times greater than the surface area of the base. The larger the differential bbtween the sur-face area of the base and the surface area of protuberances, the more difficult it becomes to remove the pile material from the mold. Because of this problem, conventional techni-ques require cooling the entire mold to a temperature signi-ficantly lower than the molding temperature before the molded piece can be removed.
In accordance with our invention, the molded product is removed from the mold without substantially reducing the temperature of the mold. In other words, the temperature at which the moIded polymeric material is removed from the mold is ~; about equal or slightly lower than the temperature at which the polymeric material is forced into the mold. Apparently, cross-linking during formation of the pile fibers greatly improves the ~, - , ~2S hot atreng~h of the molded pile product, permitting it to be re-moved from ~he mold while still hot.i In view of the large number .
of cavities making up of the mold and the relatively small diameter of these cavities, we were highly reluctant to use crosslinkable materials because if the mold became plugged, it 30~ wol~ld be very difficult to clean the mold. Surprisingly, , ~060638 pluyging of the mold does not occur if care is exerciSed.
Apparently, during crosslinking, gases seem to be generated in situ due to crosslinking to form a barrier between the internal surface of the mold cavities and the surface of the fiber being formed in the mold. This barrier, we believe, pre-vents the molded fibers from adhering to the cavity walls and also creates an internal pressure which tends to push against the fibers, forcing them from the mold cavities.
The conditions or making our pile product will vary in accordance with the starting materials used and the geometric configurations of the pile formed during molding. -Typical conditions are as follows:

CONDITIONS BROAD RANGE OPTIMUM

Temp. C 175 - 280 215 (F) (347 - 535j (420) Pressure Kg/cm2 35.2 - 175.8 120 (p.s.i.) (500 - 2500) (1700) Cycle Time - sec. 5 - 1800 60 As discussed later in greater detail~ the molding composition is preferably formed into a preform. This pre-form may be preheated prior to being placed in the mold. Care is taken when preheating the preform to prevent any significant crosslinking prior to formation of the pile product in the -mold.

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Although our method lends~ ~tself to ~mprQyed release of t~e p~le product f~om the mold, ~t ~s desirable to e~ther add a release agent to the molding composition or precoat the mold or the preform with a re-lease agent. Release agent~ added to the molding composi-tion may also facilitate blending of the ingredients during preparation of the preform. Examples of suitable release agents which may be added to the molding composi-tion are fatty acids and their amides, esters and salts.
Examples of suitable release agents for precoating the mold are silicone compounds and waxes.
A typical pile product made by our method would have fibers having an average diameter measured at the base -ranging between 0.0087 and .05 centimeter (about 0.002 and 0.020 inch), an average length ranging between 0.01 and 5 centimeters (about 0.004 and 2.00 inch), and an aspect ratio (fiber length divided by fiber diameter~ of greater than 1, preferabl~ from 1 to 200. The fiber coverage density* normally ranges from 0.10 to 0.50, and the total surface area of the fibers is at least five, pre-ferably more than ten, times greater than the surface area of .
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, ' ~ -' * Fiber Coverage Dens~ty = ~total ~olume of fibers~
(area of the base~ X (average pile height) ~ .
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~060638 the base. The cross section of the individual fibers may be, for example, circular, semi-circular, serrated or ribbed, hexagonal, octagonal, oval, triangular, rectangular, etc. The fibers may also be tapered or untapered.

Advantages The advantages of our invention are manifold. First, the time to produce a molded pile product using our method is substantially less than that required using conventional mold-ing processes. For example, a pile product having the above fiber characteristics can be molded using our method in about one minute or less. In contrast, to make a pile product of equivalent physical dimensions according to prior art processes would take in excess of five minutes. Our molding method, therefore, provides at least about a five-fold decrease in the molding cycle time.
~he second advantage of our method is that the pile product is easily removed from the mold compared to prior art processess. As mentioned above, apparently, as crosslinking ` proceeds, gases are liberated which surround the fiber and form a barrier between the mold cavities and the fibers. This `
~ barrier tends to preventthe fibers from sticking to the wall ; of the cavities. Moreover, the gas pushes against the pile product, tending to force the pile product from the mold as soon as the applied molding pressure is removed. We have ~25 observed the molded pile product made according to our process may ~
pop from the mold as soon as the molding pressure is released. ;;
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A third advantage is that the molded pile fibers may be stronger than the pile fibers produced using conventional methods. For example, ethylene vinyl acetate copolymer when molded using conventional methods provides a fiber which, when rubbed with a coin or other metal object, tends to elongate. Thus the surface of the pile product is dis-figured if a coin is rubbed across it. In contrast, when ethylene vinyl acetate copolymer is crosslinked during - molding of the fibers, such fibers resist entirely or will not be severely elongated by a coin rubbed against them.
A fourth advantage is that the mold or molded pile pro-duct cools only slightly during molding. Consequently, the mold de-sign is simplified, and since the mold is not continuously cycled be-tween extreme hot and cold temperatures,energy is conserved.
The pile product provided by our method may be specifically formulated to provide superior properties in selected performance areas. For example, pile products can be made having improved strength, resistance to solvents, high temperature stability, and/or flame retardancy.

~20~ Examples In accordance with the preferred embodiment of our invention, a thin sheet of molding composition or preform is first prepared by blending together a crosslinkable poly~eric material, a heat responsive crosslinking promoter, and other ~25 ingredients. Although the preform is preferred, pellets may also be used. The pile product is then molded from the pre-form or pellets.
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Example 1 The preform of this example is prepared using the following ingredients:
P~RTS
ethylenevinyl acetate copolymer 70 (31~ vinyl acetate, Melt Index 24 0,sp gr. 0.960, sold by United . States Industries, UE~38) low density polyethylene (~5elt 20 Index 3.3, sp.gr. 0.919, sold by United States Indus~ries,NA 226) butadiene polymer tsp.gr. 0 92, 10 made by Polysar Inc.,Taktene 1220) precipitate amorphous silica (.02 35 micron particle size, sold by PPG
Industries, HiSil 233) stearic acid 0.5 ~20 ~ ~ - biæ-~t-butyl peroxy~ 3.0 d~iæopropylbenzene (39.5 - 41.5%
active, supported on Burgess KE
clay, sold by Hercules,Inc.,Vulcup 40 KE) The polymeric material is softened and blended thoroughly 25 ~ ~ with the silica and stearic acid and then cooled to below 125C
(275F) before the addition of the free radical generating peroxide.
This mlxing is carried out in a Farrel B Banbury mixer, but other in-; t-nsive internal mixing equipment may be used. Following blending, the mlxture i8 worked into sheet form, for example, by a two roll ~;
;~ rubber mill to make the préform. The preform weight is 100 grams and 1ts dimensions are about 6in. X 6in. X 1/8in. This preform is placed ln a mold which is kept at the temperature of 420F~215C) and a preasure~ of about 1800 p.s.i.(l22Kg/cm2) is applied at thisl point.
The~mold temperature drops about i5oF(8.3oc) momentarily. After 35~- about 1 minute at this temperature (420F) and pressure (1800 p.s.i), , . .. .
the pres~ure is released and the part is removed at this temperature.
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F.xample 2 The preform of this example is prepared using the following ingredients:
~ P~RTS
low density polyethylene (Melt 338 Index 2.0, sp.gr. 0.927, sold by United States Industries, NA 294) styrene-butadiene block copolymer 422 (sold ~y Shell Chemical Co., Kraton G, GXT 6500) low density polyethylene (Melt ~21 Index 3.3, sp.gr. 0.919, sold by United States Industries, NA 226) TiO2 (anatase) 2.0 :
amorphous silica (0.040 micron 300 particle size, sold by P.P.G.
Industries, HiSil/EP) ~ -stearic acid 6.0 . trimethyol propane trimethacrylate 4.0 (sold by Sartomer Co., SR-350) peroxide compound (Vulcup 40 KE) 35 : . :
~ The above ingredients are blended together and made into a ; ~ preform and molded as generally described in Example 1.
xample 3 . .
25 : The preform of this example is pre?ared using the : following ingredients: .
~; . . PARTS -ethylene vinyl acetate copolymer . 70 ~U. S. Industries, UE-638) ~ :
low density polyethylene 20 U. S. Indus~ries, NA-226) butadiene polymer 10 Polysar, Inc., Taktene~1220) : stearic acid o.s ~ .

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~060638 PARTS
amorphous silica (P~ P G.
Industries, HiSil 233) 35 trimethylol propane trimethacrylate 2.0 (Sartomer Co., SR-350) peroxide compound ~Vulcup 40-KE) 3.0 The above ingredients are blended together and made into a preform and molded as generally described in Example l.

Example 4 The preform of this example is prepared from the following ingredients:
PARTS
low density PolYethvlene. .... . . 338 (U. S. Industries, NA 294) styrene-butadiene block copolymer 412 (Shell Chemical Co., Kraton 1107) polyethylene (U. S. Industries, NA 226) 6 si~ica (HiSil 233) 300 `
mold release agent (8umko Co.,Kenamide E) 0.9 peroxide compound (Vulcup 40 KE) 35 The above ingredients are blended together and made into a preform and molded as generally described in Example 1.

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rxample 5 The preform of this example is prepared using the following inyredients:
~ PARTS

ethylenevinyl acetate copolymer (31% vinyl acetate, Melt Index 24 0, SpGr. 0.960 sold by United States Industries, Division of National Distillers, Inc. N~638) 70 low density polyethylene (Melt Index 3.3, Sp.Gr. 0.919, sold by United States Industries, NA226) 20 butadiene polymer (SpGr. 0.92 made by Polysar, Inc., Taktene 1220) 10 stearic acid 0 5 a,~' - bis - (t-butyl peroxy) diisopropyl benzene (39.5-41.5 active,supported on Burgess KE
clay, sold by Hercules, Inc., Vulcup 40 KE) 3.0 A 6" X 6" X 1/10" preform was placed in a heated mold for preparing a molded pile product and a pressure of about 1800 poS~i~ (122 Kg/cm2) was applied. The mold temperature was initially 200F (93C) and was raised to 400F (204oc) in 25~ 4 minutes while under molding pressure, and held at 400F (204C) ; for 4 minutes. The part was essentially completely removed at ; 400F(204OC) , Example 6 ~ The preform of this example is prepared using -~ 30 ~ the following ingredients:
~ ` PARTS
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ethylene vinyl acetate copolymer ~ (31% vinyl acetate, Melt Index 24 0, -~ SpGrØ960 sold by United States 3S Industries, Division of National Disti~lers, Inc. N~638 70 ~ :

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1060~38 P~Rq'S
low density polyethylene (Melt Index 3.3, Sp.GrØ919, sold by United States Industries, NA226) 20 butadiene polymer (Sp.Gr. 0.92) made by Polysar, Inc.,Ta~tene 1220) 10 hydrated aluminum oxide, 65~ A12O3 (Aluminum Co. of America, ~Iydral C 330) 35.0 stearic acid 0.5 ~ bis ~ (t-butyl peroxy) dii~opropyl benze~e (39.5-41.5% active, supported on Burgess KE clay, sold by Hercules, Inc., Vulcup 40 KE) 3.0 The sample can be molded using the similar molding procedure as is described in~Example 5.
' Exam~e 7 The preform of this example is prepared using the following ingredients:
PARTS
Chlorinated polyethylene (48~ chlorine, Melt Viscosity 21.0, Sp.gr~1.25; sold by Dow Chemical Co. DOW CPE4814) ~ 100.0 Epoxy Resin (sold by Shell Oil Co.Epon828) 4 0 Hydrated Alumina Oxide (Hydral C-330,Alcoa) 40.0 Modified Tribasic Lead Sulfa~e (NL Industries Tribase AG) ~ 4 0 Basic Lead Soap Complex (NL Industries, Plasti~lcw PLl) - 0 5 _ Distearylthiodipropionate (American Cyanamid Co. Plastanox STDP) 1.0 ; Tetraethylene glycol Dimethacrylate (Sartomer Resin Inc. SR-209) 1.0 a, -bis-(t-butyl peroxy) diisopropylbenzene (39.5-41.5% active,supported on Burgess KE
clay, sold by Hercules Inc. Vulcup 40KE)2.5 The sample can be molded using the similar molding procedure as is described in Example 5.
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The preform of this example is prepared using the following ingxedients:
~ PARTS
Polyurethane Elastomer (sold by B.F.
Goodrich Chemical Co. Estane 58109 specially mixed material for Brunswick Corporation in orange color) 100.0 Silica (HiSil 233 PPG Industries, Inc.
15.0 Ethylene glycol dimethacrylate (Sartomer Resin Inc. SR-206) 4.0 a,a -bis-(t-butyl peroxy)diisopropyl benæene (39.5-41.5~ active, supported on Burgess KE
clay, sold by Hercules Inc. Vulcup 40XE) 4.0 The sample can be molded using the similar molding procedure as is described in Example 5. -Example 9 - ' ' .
The preform of this example is prepared using the following ingredients:
PARTS
PVC compound (sold by B.F.Goodrich Co.
Geon 8814) 200.0 Polyester elastomer (sold by E.I~DuPont Co.
25~ Hytrel 3495) 100.0 Tetraethylene ~ycol dimethacrylate (Sartomer Resin Inc SR-209) 5 0 Antimony Trioxide (25% active antimony oxide surface layer fused to a silica core, sold by N.L.Industries, Oncor-75RA) 10.0 a,a -bis- (t-butyl peroxy) diisopropyl benzene (39.5-41 5% active,supported on Burgess KE
clay , sold by Hercules Inc. Vulcup 40KE) 6.0 ~ -The sample can be molded using the similar molding procedure as is described in Example 5.

; -18-The Drawin~s The details of our method for making pile product and the pile product itself are schematically illustrated in the drawings, in which:
Figure 1 is a schematic drawing in cross-section showing a preform in a mold.
Figure 2 is a schematic drawing in cross-section showing the preform being forced into the mold.
Figure 3 is a cross sectional view taken along line 3-3 of Figure 1.
Figure 4 is an enlarged elevational view of a fragment of one of the groove strips shown in Figure 3.
Figure 5 is an enlarged plan view showing one ar-rangement of the groove strips.
Pigure 6 is an enlarged plan view showing a second arrangement of the groove strips.
Figure 7 is perspective view of the molded pile product of our invention.
Figure 8 is a c~rve showing the relationship be-~, .
~ 20 tween the temperature at which the molded pile product is ~ ::
~s~ molded and the time the pile product is cured in the mold.

Detailed Description of ~the Drawings ;~; :
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Flgures 1 and 2 illustrate in detail the method of our invention where a preform 10 prepared according to Example 1 is subjected to elevated pressure and temperature to form a molded , ,~ : .
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~060638 pile product 12 (Figure 7).
The mold 14 used to make the molded pile material 12 includes a frame 16 holding a number of parallel, tightly packed strips 18. These strips 18 are photoetched to form grooves 20 (Figure 4). The strips 18, standin,g on their edqes 22, are secured to the base 24 of the mold 14 by elongated I-bars 26 which slip into corresponding grooves 28 and 30, re-spectively, in the base 24 and the lower edges 22 of the grooved strips 18. Lateral movement of the strips is prevented by detachable sides 32. In assembling the mold 14, one of the sides 32 is detached and the strips 18 are stacked with their edges 22 resting on the base 24. Next the I-bars 26 are slipped into position. Lastly, the detached side 32 is secured as shown by fasteners 35, , The grooved strips 18 may be arranged in the mold frame 16 in two different ways. As shown in Figure 5, the grooved strips 18 may be stacked on edge, side by side, so that the smooth surface 18a of one strip abuts the grooved ~; 20 ~surface 18b of an adjacent strip. Arranging the strips 18 in this manner provides cavities 18c having a generally D-; shape cross-section.
; The aIternate way of arranging the grooved strips 18 is illustra~ed in,Flgure 6. In this case~ the grooved ~''25~ strips 18 arq arranged in pairs with each strip in a pair having the grooved surfaces 18b abutting each other face to face. When this arrangement is used, cavities 18d having a ' generally circular or oval cross section are provided.

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As illustrated in Figures 1 and 2, the grooved strip mold 14 has a companion ram 37 designed to fit closely within the high pressure molding area defined by the frame 16 and the tops of the grooved strips 18. The mold 14 and ram 37 are placed in a fast action hydraulic press and mounted in a retainer die~set (not shown) which allows rapid - and accurate compression of the preform 10 Both the mold 14 and the ram 37 are held at a controlled elevated tempera-ture. In the present example, the mold and associated ram were held at 215C(~2 8C), 420F ('5F). However, molding temperature may momentarily drop up to 8C.
The molded pile product 12 is prepared as follows:
First the press (not shown) is opened and the preform of Example 1 is placed in the preheated mold 14 on top of the grooved stips 18 as shown in Figure 1. The press is rapidly closed and a pressure of 128 KgJcm2 (1750 p.s i.) is applied for about l minute.
As illustrated in Figure 2, as the preform 10 melts, the molten composition is forced into the cavities 18c cor-~. .
responding to the fibers 15 of the pile product 12. As the ; molding composition flows into the cavities 18c, its tempera-ture is elevated above the decomposition temperature of the crosslinking promoter. Almost immediately, the free radicals are generated which initiate crosslinking of the polymeric material. Ordinarily, within from 1 to 120 seconds after -the molding composition is heated, crosslinking of the poly-meric material commences.
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The preform 10 is retained in the mold and sub-jected to pressure for a dwell period of from about 20 to about 180 seconds, usually less than two minutes maximum.
During this period the softened molding composition solidi-fies or gels due to the crosslinking of the polymeric material.
Figure-8 illustrates the relationship between mold-ing temperature and cure time. As depicted by the curve shown in Figure 8, the higher the molding temperature, the shorter the cure time. In other words high temperatures favor rapid crosslinking, permitting early removal of the pile product from the mold.
To achieve release of the pile product 12 from the mold 14, the ram 37 is elevated and nitrogen is injected be-tween the surface of the pile product and the grooved strips 18. About a 10.5 Kg/cm2(l5o p.s.i.) nitrogen release pressure is suitable flor a 6 X 6 inch preform 10. Preferably, the nitrogen flow is shut off before the ram 37 clears the frame 16.
Release temperature is about 204C (400F).
Nitrogen is introduced into the mold 14 by means ~ of an inlet 4,4 in the side of the mold. Because gas is ordinarily generated in situ during the crosslinking process,nitrogen release is not always necessary to achieve stripping of the fiber pile.
product 12 frbm the mold 14. In other words, the gases generated -during the molding and crosslinking process create an in-2~5~ ~ ternal pressure within the cavities or grooves 20 of the mold 14 which force the pile material 12 from the mold as soon as the ram 37 is elevated. To facilitate stripping, the surface of ~ -:~ . .
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the mold 14, may be coated prior to the molding operation with a release agent such as a silicone resin e.g., Rezolin 8302 sold by Hexcel Corporation.
The molded pile product 12 prepared according to our method and using the above described mold 1~ is schema-tically illustrated in Figure 7. This pile product comprises a base 12 and plurality of fibers 15 extending from the base.
The fibers 15 are characterized by being formed of a cross-linked polymeric material which was crosslinked during for-mation of the fibers. The fibers 15 may have many shapes depending upon the shapes of the cavities formed by the grooved strips 18. They may be tapered or nontapered. All the fibers - may be of equal height, or some fibers may be longer than other fibers. The fibers may have different cross sectional configurations. The fibers may be parallel to each other or randomly oriented. Or the fibers may be of the same or dif-ferent colors.
The pile product 12 is characterized by the physical dimensions - ~ of the fibers 15. The fibers 15 have an average diameter ~20 ~ measured at the base ranging between 0.0087 and 0.5 centimeter (about 0.00 2 and 0.020 inch). ~The average length of the fibers ranges between 0.01 and 5 centimeter ~about 0.004 and 2.00 inch) .
~: the aspect ratio of the fibers is greater than 1. The density of the fiber is from 0.10 to 0.50. Since the pile product ~25 ~ 12 is formed by a molding process, the base 13 and the fibers 15 are integral. After crosslinking, the elastic modulus of the polymeric material forming the fibers should range between 15 and 15,000 I Rg/cm2.
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106~)638 In accordance with the preferred embodiment of our invention, the density, diameter and length of the fibers 15 are carefully selected so that the feel of the fibers to the touch is similar to the feel of conventional pile fabrics. This feel is achieved by adjusting the fiber len~th in the fiber diameter in accordance with the elastic modulus of the crosslinked material. The higher the modulus the thinner the diameter or longer the length of ~he fiber and vice versa.

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Claims (29)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pile product comprising a base and a plurality of fibers extending from the base, said fibers having an aspect ratio greater than one and having been shaped in a mold, said fibers being formed from a molding composition including a crosslinkable polymeric material which is cross-linked during formation of said fibers, and said fibers exhibiting no material deformation.

2. The pile product of Claim 1 where the fibers have an average diameter measured at the base ranging between 0.087 and 0.05 centimeter.

3. The pile product of Claim 1 where the fibers have an average length ranging between 0.01 and 5 centimeters.

4. The pile product of Claim 1 where the fibers have density of from 0.10 to 0.50.

5. The pile product of Claim 1, Claim 2 or Claim 3 wherein the aspect ratio of the fibers is approximately between 10 and 200.

6. The pile product of Claim 1 where the crosslinkable polymeric material after being crosslinked has an elastic modulus ranging between 15 and 15,000 kilograms per square centimeter.

7. The pile product of Claim 1 where the molding composition includes a substance which on being heated promotes crosslinking.

8. The pile product of claim 1 where the molding composition includes from 10 to 99 weight per-cent polymeric material, from 0.5 to 5 weight percent of a substance which promotes crosslink-ing on being heated, from 0 to 70 weight percent of an additive, and from 0 to 70 weight percent of a polymerizable monomer.

9. The pile product of claim 8 where the polymeric material comprises a polymer, copolymer or mix-tures thereof derived from polymerizable organic compounds selected from the group consisting of (a) olefin hydrocarbons, (b) vinyl compounds, (c) diene compounds, (d) esters, and (e) urethanes,

10. The pile product of claim 8 where the major com-ponent of the polymeric material is ethylene vinyl acetate copolymer.

11. The pile product of claim 8 where the substance which promotes crosslinking is (a) a peroxide compound, (b) a mixture of a peroxide compound, silicon compound and a catalyst, (c) and azo compound, or (d) a mixture of zinc oxide and sulfur.

12. A pile product comprising a base and a plurality of fibers extending from the base, said fibers having an average diameter measured at the base ranging between 0.01 and 0.05 centimeter, an average length ranging between 0.01 and 5 centimeters, a density of from 0.10 to 0.50, an aspect ratio of greater than one, said fibers having been shaped in a mold and said fibers having been formed from a molding composition including a crosslinkable polymeric material which is cross-linked during formation of said fibers and, after being crosslinked, has an elastic modulus ranging between 50 and 15,000 kilograms per square centimeter, and said fibers having been given no material deformation or elongation due to their removal from the mold.

13. The pile product of Claim 12 where the diameter and length of the fibers are selected so that the feel of the fibers to the touch is similar to the feel of conventional pile fibers.

14. The pile product of Claim 13 where the molding composition includes from 10 to 99 weight percent polymeric material, from 0.5 to 5 weight percent of a substance which promotes crosslinking on being heated, from 0 to 70 weight persent of an additive, and from 0 to 70 weight percent of a polymerizable monomer.

15. The pile product of claim 14 where the polymeric material comprises a polymer, copolymer or mix-tures thereof derived from polymerizable organic compounds selected from the group consisting of (a) olefin hydrocarbons, (b) vinyl compounds, (c) diene compounds, (d) esters, and (e) urethanes.

16. The pile product of claim 14 where the major component of the polymeric material is ethylene vinyl acetate copolymer.

17. The pile product of claim 14 where the substance which promotes crosslinking is (a) a peroxide compound, (b) a mixture of a peroxide compound, silicon compound and a catalyst, (c) and azo compound, or (d) a mixture of zinc oxide and sulfur.

18. A method making a pile product comprising the steps of (a) subjecting a molding composition including a crosslinkable polymeric material to an elevated temperature and pressure to force the polymeric material into a mold having a plurality of cavities corresponding to the fibers of the pile product; and (b) with the formation of the fibers according to step (a), initiating crosslinking of the polymeric material, and (c) removing said molded crosslinked polymeric material from the mold at a temperature which is about equal or slightly lower than the temperature of step (a)

19. The method of claim 18 where the fibers being formed have an average diameter measured at the base ranging between 0.0087 and 0.05 centimeter, and an average length ranging between 0.01 and 5 centimeters, a density of from 0.10 to 0.50, and an aspect ratio of greater than one.

20. The method of claim 19 where the temperature ranges between 175 and 280°C, and the pressure ranges between 35.2 and 175.8 kilograms per square centimeter.

21. The method of claim 20 where the molding cycle ranges between 5 and 1800 seconds.

22. The method of claim 21 where the molding composition includes from 10 to 99 weight percent polymeric material, from 0.5 to 5 weight percent of a sub-stance which promotes crosslinking on being heated, from 0 to 70 weight percent of an additive, and from 0 to 70 weight percent of a polymeriable monomer.

23. The method of claim 22 where the polymeric material comprises a polymer, copolymer or mixtures thereof derived from polymerizable organic compounds selected from the group consisting of (a) olefin hydrocarbons, (b) vinyl compounds, (c) diene compounds, (d) esters, and (e) urethanes.

24. The method of Claim 22 where the major component of the polymeric material is ethylene vinyl acetate copolymer.

25. The method of Claim 22 where the substance which promotes crosslinking is (a) a peroxide compound, (b) a mixture of a peroxide compound, silicon compound and a catalyst, (c) and azo compound, or (d) a mixture of zinc oxide and sulfur.

26. The pile product of Claim 4, Claim 6 or Claim 8 wherein the aspect ratio is approximately between 10 and 200.

27. The pile product of Claim 9, Claim 10 or Claim 11 wherein the aspect ratio is approximately between 10 and 200.

28. The pile product of Claim 12, Claim 13 or Claim 14 wherein the aspect ratio is approximately between 10 and 200.

29. The pile product of Claim 15, Claim 16 or Claim 17 wherein the aspect ratio is approximately between 10 and 200.