FIELD OF THE INVENTION

The present invention relates to a composition for carpet backing, in particular to a composition comprising a polyolefin and a filler. The present invention also relates to a carpet comprising the carpet backing composition and to a method for making the carpet comprising the carpet backing composition.

BACKGROUND OF THE INVENTION

Most conventional carpets comprise a primary backing layer with fiber tufts in the form of cut or uncut loops extending upwardly from the primary backing layer and a secondary backing layer at the backside of the primary backing layer.

US2004/0052952 discloses a process for tuft and filament binding to an unfinished carpet, which comprises applying a coating composition which comprises from 50% to 100% by weight of one or more substantially amorphous poly-alpha-olefins as a melt to the backside of the unfinished carpet in a coating weight amount of from 20 to 1,500 g/m2to bind the tuft and filament to the unfinished carpet, wherein the melt viscosity of the coating composition at 190° C. is from 200 mPas to 20,000 mPas.

The poly-alpha-olefin comprises polymerized monomer units of from 0% to 100% by weight of one or more alpha-olefins having 4 to 10 carbon atoms, from 0% to 100% by weight of propene and from 0% to 20% by weight of ethene.

The coating composition further comprises one or more of from 0% to 5% by weight of a crystalline polyolefin, from 0% to 35% by weight of fillers or pigments, and from 0% to 15% by weight of a wax.

US 2008/0280093 discloses a carpet comprising:a primary backing material;a plurality of fibers attached to the primary backing material; andan adhesive composition, wherein the adhesive composition comprises at least one homogenously branched ethylene polymer characterized as having a short chain branching distribution index of greater than or equal to 50%, and a filler in an amount comprised between 1 and 75 weight percent of the composition, wherein the adhesive composition has substantially penetrated and substantially consolidated the fibers.

Preferably the ethylene polymers are substantially amorphous or totally amorphous. Representative examples of fillers include, but are not limited limestone (primarily CaCO3), marble, quartz, silica, and barite (primarily BaSO4). Suitable particle sizes range from about 1 to about 50 μm.

JPH05132870 discloses a resin composition for backing tile carpets, obtained by blending:100 parts by weight resin component composed of (A) 50-90% by weight amorphous polyolefin and (B) 10-50% by weight tackifier (e.g. natural rosin or a modified rosin) with (C) 0-30 parts by weight of crystalline polypropylene and25-900 parts by weight filler containing magnesium carbonate.

The particle size of MgCO3filler is between 1 and 500μ, preferably between 10 and 300 μm. The polyolefin can be a random copolymer of ethylene and propylene, wherein the ethylene content is between 0 and 30% by weight.

US 2014/0017439 describes carpets comprising:a primary backing layer having a face side and a back side;a plurality of fibers attached to the primary backing layer; anda second layer attached to the back side of the primary backing layer, comprising at least one propylene-based elastomer, with limited crystallinity, comprising at least about 60% by weight propylene-derived units and about 5 to about 25% by weight ethylene-derived units.

The backing layers may include up to 80% by weight, based on the total weight of the layer, of organic and/or inorganic fillers. Suitable fillers are calcium carbonate, aluminum trihydrate, talc, among others.

U.S. Pat. No. 7,741,397 discloses a polymer composition comprising an ethylene/alpha-olefin interpolymer and a filler. The ethylene/alpha-olefin interpolymer is a block copolymer having a certain amount of crystallinity, and the filler, with a particle size preferably comprised between 3.2 and 8 μm, is present in the polymer composition in an amount comprised between 30 and 95%. The polymer composition can be used in automotive flooring applications.

US 2010/0285246 discloses a polyolefin for floor coverings, wherein the polyolefin contains not more than 20% by weight of ethylene, either 70-100% by weight or not more than 20% by weight of propylene and/or either 70-100% by weight or not more than 20% by weight of 1-butene or of another linear 1-olefin, with the sum of the proportions being 100% by weight, and the triad distribution for propene triads determined by 13C-NMR has an isotactic proportion of 75-98% by weight, an atactic proportion of less than 20% by weight and a syndiotactic proportion of not more than 20% by weight and/or the triad distribution for 1-butene triads determined by 13C-NMR has an isotactic proportion of 10-98% by weight, an atactic proportion of 1-85% by weight and a syndiotactic proportion of not more than 20% by weight.

The polyolefin may be mixed with not more than 80% by weight of inorganic and/or organic, based on a hot melt formulation comprising polyolefin and filler.

WO2015/100073 discloses a carpet comprising:(a) a primary backing layer;(b) a plurality of fibers attached to the primary backing layer; and(c) a second layer attached to the back side of the primary backing layer, wherein at least one of the primary backing layer and the second layer comprises a polymer blend comprising:(i) a first propylene-based polymer, wherein the first propylene-based polymer is a homopolymer of propylene or a copolymer of propylene and ethylene or a C4 to C10 alpha-olefin; and(ii) a second propylene-based polymer, wherein the second propylene-based polymer is a homopolymer of propylene or a copolymer of propylene and ethylene or a C4 to C10 alpha-olefin; wherein the second propylene-based polymer is different than the first propylene-based polymer;
wherein the polymer blend has a melt viscosity, measured at 190° C., according to ASTM D-3236, of about 500 to about 25,000 cP. Any one of the layers can comprise a filler and/or additive. The filler may be present at up to about 80% by weight, based on the total weight of the layer. The polymer blend may have a heat of fusion comprised between 5 J/g and less than 90 J/g and a crystallization temperature of greater than 0° C. and less than 110° C.

US 2016/0102429 discloses a carpet backing composition comprising:(a) 10 to 50% by weight of a first polymer component, the first polymer component comprising an elastomeric polymer;(b) 50 to 90% by weight of a filler; and(c) 0.1 to 5% by weight of a compatibilizer, the compatibilizer providing free radical source to bond the first polymer component and the filler.

The filler comprises fly ash, ground glass, calcium carbonate, talc, clay, or combinations thereof. The first polymer component is a propylene-based copolymer having:75 to 95% by weight propylene-derived units and about 5 to 25% by weight units derived from at least one of ethylene or a C4 to C12 alpha-olefin;a heat of fusion, as determined by DSC, of about 75 J/g or less;a percent crystallinity of 2 to 65.

The composition may further comprise a second polymer component. The second polymer component can be a homo-polymer, such as a functionalized/modified homo-polymer, a copolymer, such as a functionalized/modified copolymer, an oligomer, a hydrocarbon tackifying resin, such as a functionalized/modified hydrocarbon tackifying resin, or any combinations thereof.

Carpets, during their use, are subject to atmospheric fluctuations such as changes in ambient temperature and humidity, which endanger their dimensional stability. To remedy to the dimensional instability and to prevent curling, a flexible backing is indispensable; yet it is generally known that the flexibility of the polymer(s), forming the backing layer, is negatively influenced by the addition of filler and additives. Fillers are added to the formulation both for economical and performance reasons e.g. fire resistance.

The negative effect of filler on the flexibility of a polyolefin/filler blend, depends on the particle size of said filler and is proportional to it. Otherwise, low particle size fillers negatively influence processing of the blend since they give rise to local overheating of the polyolefin causing degradation of the polymer resulting, dependent on the polymer composition, in either an increase in viscosity due to peroxide-initiated crosslinking or a loss in physical properties of the backing layer due to chain scission.

In particular, polymers containing high levels (more than 50% in weight) of ethene are subject to a viscosity increase during high temperature processing due to crosslinking degradation, causing poor processing performances especially for high filled compounds. Contrary, polymers containing high level of C3 to C8 monomers have no tendency to crosslink during hot processing. In addition, high amounts of low particle size filler negatively influence the adhesion of the backing layer to the unfinished carpet.

AIMS OF THE INVENTION

The present invention aims at providing a carpet backing layer that does not present the drawbacks of the prior art carpet backing layers. In a further aspect, it is an aim of the present invention to provide a carpet backing layer allowing the production of carpets showing a dimensional stability independent of atmospheric conditions, the carpet backing layer being applicable by a trouble-free process. An aim of a further aspect of the invention is to provide a method for the production of carpets, comprising the carpet backing layer as well as the carpet itself.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention relates to a carpet backing layer composition comprising:between at least 10% by weight and 50% by weight or less, preferably 40% by weight or less, more preferably 30% by weight or less, most preferably 20% by weight or less of a semi-crystalline polyolefin or of a blend of two or more semi-crystalline polyolefin(s) said polyolefin or blend of two or more polyolefins being characterized in that the weight percentage of (co)polymerized C2 olefin is less than 50 and that the weight percentage of C3-C8 alfa olefins is 50 or more; andbetween up to 90% by weight and 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, most preferably 80% by weight or more of one or more inorganic filler(s) characterized by a volume median particle diameter (D50) comprised between up to 1000 μm and at least 10 μm, preferably more than 20 μm, more preferably more than 50 μm and most preferably more than 100 μm, or even more than 200 μm as obtained from laser light scattering measurements according to ISO 13320;
the backing layer composition being characterized in that the heat of fusion within the temperature range of from 10 to 40° C. (ΔH10→40° C.) is less than 12.5%, preferably less than 10%, more preferably less than 5% of the heat of fusion within the temperature range of from 10 to 170° C. (ΔH10→170° C.) the heat of fusion being measured by Differential Scanning calorimetry.

Preferred embodiments of the present invention disclose one or more of the following features:the polyolefin or blend of polyolefins has a Shore A hardness, according to ASTM D 2240 of at least 65, preferably of at least 70, more preferably of at least 75, most preferably of at least 80, even of at least 85 or even of at least 90;the C3-C8 alpha-olefin(s) of the one or more polyolefin(s) are selected from the group consisting of the isomers of C3 to C8 alpha-olefins and combinations thereof;the C3-C8 alpha-olefin of the one or more polyolefin(s) is propene, 1-butene, 1-octene or a combination thereof;the polyolefin is selected from the group consisting of polypropylene, poly-1-butene, propene-ethene copolymer, propene-1-butene copolymer, 1-butene-ethene copolymer, propene-1-butene-ethene copolymer and 1-octene-ethene copolymer;the inorganic filler is selected from the group consisting of talc, mica, calcium carbonate, magnesium carbonate, dolomite, barite (barium sulfate), bauxite, magnesium hydroxide, aluminium hydroxide, kaolin, silica, glass, and any combination thereof;the carpet backing layer composition comprises one or more processing additive(s) selected from the group consisting of waxes, oils and tackifiers;the carpet backing layer composition comprises:between at least 10% by weight and 50% by weight or less, preferably 40% by weight or less, more preferably 30% by weight or less, most preferably 20% by weight or less of I, preferably of II, more preferably of III, most preferably of IV; andbetween up to 90% by weight and 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, most preferably 80% by weight or more of one or more inorganic filler(s) characterized by a volume median particle diameter (D50) comprised between up to 1000 μm and at least 10 μm, preferably more than 20 μm, more preferably more than 50 μm and most preferably more than 100 μm, or even more than 200 μm as obtained from laser light scattering measurements according to ISO 13320;wherein:I. comprises 20% by weight or more of one or more polyolefin(s) and 80% by weight or less of one or more processing additive(s);II. comprises 25% by weight or more of one or more polyolefin(s) and 75% by weight or less of one or more processing additive(s);III. comprises 35% by weight or more of one or more polyolefin(s) and 65% by weight or less of one or more processing additive(s);IV. comprises 45% by weight or more of one or more polyolefin(s) and 55% by weight or less of one or more processing additive(s);the carpet backing layer composition comprises:between at least 10% by weight and 50% by weight or less, preferably 40% by weight or less, more preferably 30% by weight or less, most preferably 20% by weight or less of V, preferably of VI, more preferably of VII; andbetween up to 90% by weight and 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, most preferably 80% by weight or more of one or more inorganic filler(s) characterized by a volume median particle diameter (D50) comprised between up to 1000 μm and at least 10 μm, preferably more than 20 μm, more preferably more than 50 μm and most preferably more than 100 μm, or even more than 200 μm as obtained from laser light scattering measurements according to ISO 13320.wherein:V. comprises 55% by weight or more of one or more polyolefin(s) and 45% by weight or less of or more processing additive(s);VI. comprises 65% by weight or more of one or more polyolefin(s) and 35% by weight or less of one or more processing additive(s);VII. comprises 80% by weight or more of one or more polyolefin(s) and 20% by weight or less of one or more processing additive(s);the carpet backing layer composition is characterized by a melt viscosity at 160° C. in a rotational viscometer, according to ISO 11443, of from 10 Pas to 5000 Pas, preferably from 20 Pas to 2500 Pas, more preferably from 50 to 500 Pas.

In a further aspect, the present invention relates to a carpet comprising a carpet backing layer comprising the carpet backing layer composition of the present invention.

Preferred characteristics of the carpet according to the present invention comprise:the backing layer has a surface density comprised between 1600 and 4000 g/m2, preferably between 1700 and 3500 g/m2, more preferably between 1800 and 3000 g/m2, most preferably between 1900 and 2500 g/m2andthe backing layer thickness is comprised between 0.4 and 4.0 mm, preferably between 0.5 and 3.5 mm, more preferably between 0.7 and 2.5 mm, most preferably between 0.8 and 2.0 mm.

The present invention further discloses a method of making a carpet comprising:a) extrusion coating the carpet backing layer composition of the present, on the back side of a primary backing material, said primary backing material having a face and a back side, a plurality of fibers attached to the primary backing material and extending from the face side and exposed at the back side andb) cooling down the carpet layer composition and forming the carpet backing layer.

Preferred embodiments of the method of making a carpet further disclose:the extrusion coating is performed at a temperature comprised between 130 and 170° C., preferably between 140 and 160° C.an additional step comprises subjecting the extrusion coated carpet backing layer composition of step a) to a subsequent heat treatment at a temperature comprised between 130 and 170° C., preferably between 140 and 160° C. for a time period comprised between 1 and 60 s, preferably between 5 and 30 s, more preferably between 10 and 20 s, before cooling down in step b).

