THERMOFORMABLE CARPET BACKING COMPOSITION AND A PROCESS OF MAKING A CARPET

Abstract: A thermoformable carpet backing composition having good flexibility at a specified coating weight, good melt strength, good hot melt adhesiveness, resistance to cracking when flexed at low temperatures and shape retention after thermoforming comprising: (A) about 16 to 35% based on the total weight of the composition of an ethylene copolymer having about 70 to 90% by weight of copolymer of ethylene copolymerized therein, selected from the group consisting of ethylene/vinyl aliphatic acid esters copolymers having about 1 to about 4 carbons in the aliphatic acid; and ethylene/alkyl acrylate copolymers having about 1 to about 18 carbons in the alkyl moiety, said ethylene copolymer having a melt index of 0.5 to 12 based on ASTM-D-1238-E, (B) about 65 to 80%, based on the total weight of the composition of filler containing at least 55% based on the total weight of filler of barium sulfate, and (C) from 0 to about 8% based on the total weight of the composition of a non-water-soluble plasticizer. Also disclosed is a process for forming a carpet backing using compositions of the present invention.

Description: This invention relates, in general, to carpet backing compositions, and more specifically to thermoformable carpet backing compositions containing a thermoplastic. Compositions of the present invention are especially suitable for extrusion onto the back of automobile carpets. Automobile carpet is typically produced in the form of a tufted carpet backsized with a laver of polyolefin. The tufted carpet has a front surface which is exposed to the automobile's interior and a back surface. A carpet backing composition, the subject of the present invention, is then extruded through a slot die onto the back surface of the tufted carpet so as to form a layer. A non-woven pad is then attached to the remaining exposed surface of the carpet backing composition. It is known to use filled polyethylene copolymer compositions as the carpet backing. However, such compositions have difficulty meeting all the specifications required to make good automotive carpet. Two important properties of carpet backing compositions are weight and stiffness. Weight is defined as the weight of the composition in lbs/ft2 after it has been extruded onto the sized tufted carpet. The thickness of the composition is not taken into account in measuring weight, since only the weight in lbs/ft2 of extruded composition determines the value of this important property. Hence, in order to meet minimum weight specification, typically about 0,6 lb/ft2, the carpet backing composition is extruder onto the sized tufted carpet at whatever thickness is necessary to provide sufficient weight. Carpet manufacturers demand that carpet backing composition have a high weight in order to decrease the sound transmitted through the carpet. Automobile carpeting, should have low stiffness so that the carpet may easilv be handled for insertion into the automobile and so that the carpet conforms to the shape of the floor pan. Since the stiffness of the carpet is directly proportional to the cube of the carpet's thickness, it is very difficult to meet both weight and stiffness requirements. If the thickness of the composition is increased in order to meet minimum weigh requirements, the stiffness is drastically increased and vice versa. Typical prior art compositions comprising ethylene copolymer and calcium carbonate filler have not been able to simultaneously meet both weight and stiffness t requirements. Other desirable properties for carpet backing compositions are melt sJenght, hot melt adhesiveness, resistance to cracking when flexed at low temperature, and shape retention after thermoforming. Accordingly, it is an object of the present invention to provide a thermoformable carpet backing composition having both high weight and low stiffness of the finished carpet. It is another object of this invention to provide a carpet backing composition having high weight, low stiffness, good melt strenght, hot melt adhesiveness, resistance to cracking when flexed at low temperatures, and shape retention after thermoforming. These and other objects which will be readily evident to those skilled in the art are achieved by the present invention, one aspect of which comprises: a thermoformable carpet backing composition having good flexibility at a specified coating weight, good melt strenght, good hot melt adhesiveness, resistance to cracking when flexed at low temperatures and shape retention after thermoforming comprising: (A) about 16 to 35,' based on the total weight of the composition of an ethylene copolymer having about 70 to 9096 by weight of copolymer of ethylene copolymerized then, selected from the group consisting of ethylene/ vinyl aliphatic acid esters copolymers having about 1 to about 4 carbons in the aliphatic acid; and ethylene/alkyl acrylate copolymers having about 1 to about 18 carbons in the alkyl moiety, said ethylene copolymer having a melt index of 0,5 to 12 based on ASTM-D-1238-E, (B) about 65 to 8096 based on the total weight of the composition of filler containing at least 55,' based on the total weight of filler of barium sulfate, and (C) from 0 to about 8% based on the total weight of the composition of a non-water-soluble plasticiser. A second aspect of the invention comprises a process for making a carpet using compositions of the present invention Figure 1 is a ternary diagram illustrating preferred compositions of the present invention. Figure 2 is an illustration of a typical automobile carpet. This invention is predicated upon the discoverv that compositions containing barium sulfate falling within a relatively narrow composition range,have a surprising combination of good properties including low stiffness, high weight, good melt strenght, hot melt adhesiveness, resistance to cracking when being flexed at low temperatures, and shape retention after thermoforming. Compositions of the present invention are comprised of ethylene copolymer, filler and plasticizer with optional anti-oxidants. Each of these ingredients is described in detail below. METHYLENE COPOLYMER The composition must contain about 16 to about 35% based on the total weight of the composition of ethylene copolymer, preferably 20 to 3096, and most preferably 23 to 25%. The ethylene copolymers should have 70 to 90% by weight of the copolymer of ethylene copolymerized with ethylene vinyl aliphatic acid esters having about 1 to about 4 carbons in the aliphatic acid, or ethylene alkyl acrylate copolymers having about 1 to about 18 carbons in alkyl moiety. Th ethylene copolymers must have a melt index of 0,5 to 12 based on ASTM-D-1238-E. The most preferable ethylene copoly mer is ethylene ethyl acrylate copolymer having about 84 to 86% by weight of copolymer of ethylene copolymerized with the ethyl acrylate and having a melt index of 1.0 to 1,6. This product is sold commercially from Union Carbide Corporation under the tradename Bakelite DPDA - 6182. Good results are also obtained if the ethylene ethvl acrylate copolymer has about 83 to 87% ethylene copolymerized therein. Other suitable copolymers include ethylene vinyl acetate, ethylene vinyl formate, ethylene vinyl propionate, ethylene vinyl butyrate and ehtylene butyl acrylate copolymers. FILLER The critical ingredient in the filler is barium sulfate. The filler must contain at least 55 weights barium sulfate basec on the total weight of filler, and preferably at least 75,' barium sulfate. The most preferable filler is commercially pure barium sulfate, (which currently contains about 80 weight% BaS04) pulverized grade, having a specific gravity of 4,0 to 4,3 and a particle size of 2 to 2,5,' retained on 200 mesh and 85 to 9096 retained on 325 mesh (weighty cumulative). Filler meeting these requirements is sold by Dresser Minerals under the tradename "BARITE No. 85". Filler containing more than 80 weight barium sulfate, would give better results, however, as shown by the examples to follows compositions containing BARITE No. 85 are completely satisfactory. PLASTICIZERS The plasticizers used with the present invention must be non-water-soluble. Suitable plasticizers include estertype plasticizers such as dimethyl phthalate and dibutyl phthalate, as well as phosphate-type plasticizers such as tributyl, tributoxyethyl, tricreasyl, triphenyl, diphenyl, octyl and diphenyl cresyl phosphates. The preferred plasticizers include napthenic oil, paraffin oil, aromatic oil and mixtures thereof having a viscosity range of 40 to 7000 SUS and more preferably 300 to 2500 SUS at 1000F. It is possible'to dilute or replace the oil with hydrocarbon tackifier resins consisting of aliphatic, aromatic or rosin derivatives having a softening point of 100 to 350C when used as a total replacement for the oil. When used to replace up to 50% of the oil, the hydrocarbon resin softening points can be from 100 to 1000C. Hydrocarbon resins are more fully described in US-patent No. 3,914,489 (column 2, lines 34 to 52) and 3,023,200, both of which are incorporated herein by reference. The most preferred plasticizer is a napthenic oil available commercially by the tradename TUFFLO 1800 sold by Atlantic-Richfield Comp. having a viscosity range of 1750 to1850 SUS at 1000F. The preferred hydrocarbon resin is an aromatic hydrocarbon resin sold under the tradename PICCOVAR AP25 bv Hercules. The amounts of plasticizer will be O to 8%, preferably 0 to 6,' and most preferably 3 to 5% based on the total weight of the composition. ANTI-OXIDANTS The choice of anti-oxidants is optional. A hindered phenol such as 4,4' methylene bis(2,6 di-tert. butylphenol) or o-tert. butyl phenol is preferred. The most preferred anti-oxidant is tetrakis (methylene (3,5-bi-tert-butyl-4 hydroxy) hydrocinnamateo sold under the tradename IRGANOX 1010 by Ciba-Geigy. Typically, 500 to 1000 parts per million (ppm) by weight based on the total weight of copolymer and oil would be used. Figure 1 is a ternary diagram illistrating preferred composition ranges for the invention. Curve A bounds a preferred general range of compositions based upon the total weight of copolymer, plasticizer, and commercially pure, i.e. about 80 weight,', barium sulfate. Curve B bounds a trit angular area of the most preferred composition range for the present invention, again based upon the weight of copolymer, plasticizer, and commercially pure barium sulfate. Small amounts of additives, such as anti-oxidants, may be added to the compositions shown in Figure 1, provided they do not adversely affect the properties of the composition. If the compositions shown in Figure 1 are not followed, the following adverse results are encountered. Compositions deviating from the region bounded by curve A in the direction of x, that is compositions containing too much barium sulfate, will have poor processing properties, especially increased viscous heating. If the composition bounded by curve A is deviated from in direction y, that is, if too much plasticizer is used, it will exhibit increased sag at the extrusion die, increased fuming, and increased sweat-ou of the filler. If too much copolymer is used, i.e. if curve A is departed from in the direction of arrow z, then the composition will contain too much polymer to be economical. Compositions of the present invention may be prepared bv mixing the ingredients in any device capable of blending thermoplastics with fillers, such as Brabender or Banbury mixers or two-roll mills. Figure 2 illustrates the method by which the compositions of the present invention are incorporated into a typical automoblie carpet. The carpet is shown positioned as it would be during manufacture, which is up-side-down with respect to its position as installed on the floor of an automobile. The carpet may be produced as follows. First tufts 1 are looped into scrim 2. Then a layer of sizing 3, typically a thermoplastic, is extruded over one side of the tufts in order to hold the tufts in place on the scrim. The combination of tufts 1, scrim 2 and sizing 3, called a sized tufted carpet 4, has a front surface 5, which would be exposed on the interior of the automobile, and a rear surface 5A. Carpet backing composition, the subject of the present invention, is extruded onto back surface 5A of sized tufted carpet 4 so as to form a layer 6 on the back surface. The layer will have an exposed surface 7. Finally, non-woven pad 8 is attached to exposed surface 7 of layer 6. This is preferably accomplished with the layer 6 of the composition in the molten state. Since the composition has good hot melt adhesiveness, non-woven pad 8 will adhere to exposed surface 7 of carpet backing composition layer 6 without use of other adhesives. E X A M P L E S Carpet backing compositions were prepared from the ingredients shown in Table I by mixing the ingredients in a two-roll mill. The compositions were then pressed into flat sheets having a weight of 0,6 lbs/ft2. The properties of the pressed compositions were as shown in Table I. The pliability test performed on Examples 2 and 5, which is in accordance with specifications of a major automobile manufacturer, was performed as follows. Eight samples of 1' x 3" carpet (consisting of sized tufted carpet and backings but without non-woven pad) were prepared. Four samples had the tufts runnung parallel with the 3" dimension and 4 had the tufts perpendicular to the 3" dimension. Each sample was inserted, pile up, into a Tinius Olsen Stiffness Tester (Model 88600 - 6 in. lb. capacity with 0.5 ib. additional weight) and secured in place. The machine was adjusted until the sample just touched the deflecting arm and zero pointer. The machine was started and the reading was taken when the pointer reached 20 . The results were averaged. A value below 35 is acceptable. The relative stiffness test, which was performed on the pressed carpet backing composition only (excluding the non-woven pad and sized tufted carpet), was performed l as follows. First the test specified by ASTM-747-70: stiffness in flexure at 23 0C was performed. This gave a modulus E in MPa. Next the relative stiffness was calculated by multiplying E by the cube of the thickness of the compositions (necessary to achieve 0.6 Ib/ft2 weight) in meters to obtain the relative stiffness in N.m. Previous correlations indicate thet a value below 1 N.m. is acceptable. It can be seen that Examples 1, 3 and 4 which comprise compositions in accordance with the present invention all had relative stiffness below the maximum acceptable for this type of composition, but the control composition of Example 5, which is typical of the prior art, had too high a relative stiffness. Example 2, also in accordance with the present invention, had pliability below the maximut acceptable value of 35 and well below that of the prior art' composition of example 5. Furthermore, all compositions of the present invention meet the other specifications required of automotive carpet backing compositions. TABLE I EXAMPLE NO. 1 2 3 4 5 CaCO3 - - - 20% 55% BaSO4 (BARITE No. 85) 70% 72% 80% 50% Ethylene Ethyl Acrylate Copolymer (1) 27% 24% 18% 27% Ethylene Vinyl Acetate Copolymer (2) - - - - 45% Aliphatic Oil (3) 3% - - 3% Napthenic Oil (4) - 4% 1% - Hydrocarbon Resin (5) - - 1% - Antioxidant (6) (Parts per million based on total weight of copolymer and plasticizer) 750 750 750 750 750 Relative stiffness at 0.6 lb/ft2 weight N m 0.54 - 0.51 0.93 2.19 Pliability of carpet without non-woven pad - 28 - - 60 Cold crack at -20 C (loop) pass pass pass pass pass Visible Fuming at normal extrusion temperature none none none none none Pad adhesion good good good good good Shape retention good good good good good Weight of layer, lb/ft2 0.6 0.6 0.6 0.6 0.6 TABLE I (Continued) (1) 15% Ethyl Acrylate based on weight of copolymer. Melt index of about 1.5 (2) 18% Vinyl Acetate based on weight of copolymer. Melt index of about 2.5 (3) Viscosity of about 335 SUS at 100 F (4) Viscosity of about 2100 SUS at 100 F (5) Piccovar AP 25 (6) Hindered phenol, IRGANOX 1010 The percentage of filler, ethylene copolymer and plasticizer are based on the total weight of filler, ethylene copolymer and plasticizer.

Claims: What is claimed is: 1. A thermoformable carpet backing composition having good flexibility at a specified coating weight, good melt strength, good hot melt adhesiveness, resistance to cracking when flexed at low temperatures and shape retention after thermoforming comprising: (A) about 16 to 35 %,.preferably about 20 to 30 %, based on the total weight of the composition of an ethylene copolymer having about 70 to 90 % by weight of copolymer of ethylene copolymerized therein, selected frog the group consisting of ethylene/vinyl aliphatic acid esters copolymers having about 1 to about 4 carbons in the aliphatic acid; and ethylene/alkyl acrylate copoly mers having about 1 to about 18 carbons in the alkyl moiety, said ethylene copolymer having a melt index of 0.5 to 12 based on ASTM-D-1238-E, (B) about 65 to 80 %,preferably about 70 to 75 %, based on the total weight of the composition of filler containing at least 55 % based on the total weight of filler of barium sulfate, and (C) from 0 to about 8 %, preferably 0 to 6 %, based on the total weight of the composition of a non water-soluble plasticizer. 2. The composition of claim 1 wherein the filler is com mercially pure barium sulfate and the weight percentages I of ethylen copolymer, filler and plasticizer based on the total weight of ethylene copolymer, filler and plasticizer fall within the area bounded by curve A or curve B of Figure 1. 3.. The compositions of one or more of the claims 1 - 2 wherein the filler is at least 75 % barium sulfate based on the total weight of the filler,or commercially pure barium sulfate. 4. The composition cf one or more of the claims 1 - 3 wherein the ethylene copolymer is ethylene/ethyl acry late copolymer having preferably about 83 to 87 % by weight of ethylene copolymerized therein. 5. The composition of one or more of the claims 1 - 4 wherein the ethylene copolymer is ethylene butyl acrylate 6. The composition of one or more of the claims 1 - 3 wherein the ethylene copolymer is selected from the group consisting of ethylene/vinyl acetate, ethylene/vinyl formate, ethylene/vinyl propionate, and ethylene/vinyl butyrate copolymers. 7. The composition of one or more of the claims 1 - 6 containing an effective amount of antioxidant. 8. The composition of one or more of the claims 1 - 7 wherein the plasticizer is selected from the group con sistin of hydrocarhon oils,preferably from the group consisting of naphthenic oil, paraffinic oil, aromatic oil and mixtures thereof having a viscosity of about 40 to 7000 SUS,preferably 300 to 2500 SUS, at 1000F, hydro carbon tackifier resins, having a softening point of 10 to 350 C or mixtures thereof wherein the hydrocarbon resin has a softening point of 10 to 1000C. 9. A thermoformable carpet backing composition having good flexibility at a specified coating weight, good melt strength, good hot melt adhesiveness, resistance to cracking when flexed at cold temperatures, and shape retention after thermoforming comprising: (A) about 23 to 25 % based on the total acrylate weight of the composition of ethylene/ethyl acrylate having about 84 to 86 % by weight of copolymer of ethylene copolymerized therein, said ethylene copolymer having a melt index of 1.0 to 1.6 based on ASTM-D-1238-E, (B) about 71 to 73 % based on the total weight of the composition of commercially pure barium sulfate, (C) about 3 to 5 % based on the total weight of the composition of naphthenic oil plasticizer having a viscosity range of 1750 to 1850 SUS at 100 F, (D) an effective amount of hindered phenol anti oxidant. 10. A process of making a carpet comprising the steps of: (A) forming a sized tufted carpet having a front surface and a back surface, (B) extruding the composition of one or more of the claims 1 - 7 onto the back surface of said sized tufted carpet so as to form a layer on the back surface thereof, said layer having-an exposed surface and if desired, (C) attaching a non-woven pad to the exposed surface of said layer.

Inventors: DELVAUX, MARIE-JOSE, MAYER, WALTER PAUL
Applicants: UNION CARBIDE CORPORATION
Application year: 1980
Main classification: D06N7
IPC codes: C08K3, C08L7, C08L33, C09D123, C08L101, C08L23, D06N7, C08L21