FIELD OF THE INVENTION

The present invention relates to an anti-tack formulation that uses primarily talc that has been cationic polymer treated for the dip slurry coating of uncured rubber compounds in anti-tack applications.

BACKGROUND ART

In the prior art, it is known to use anti-tack formulations directed to coating uncured rubber compounds. Such formulations are applied to uncured rubber to serve as a process aide. The applied coating keeps the uncured rubber slabs or pellets from sticking to itself (i.e., prevents blocking) thereby enabling the rubber compounder to more easily handle, stack or convey the uncured rubber to other unit operations such as the compression molds and to profile extrusion units.

In general terms, anti-tack formulations commonly employ a number of ingredients such as mineral pigments, swelling clays, metallic stearate pigments, alkali metal fatty acid soaps, nonionic surfactants, defoamers, pigment suspension aides, waxes, etc. Some of the prior art also discloses the use of various water soluble polymer additives to enhance the coating film properties of the applied anti-tack. Examples of water soluble polymer additives employed in the prior art are:carbohydrate based polymers like carboxyl methyl cellulose (CMC) or polysaccharides (like xanthan gums);nonionic polymers like polyvinyl alcohol (PVA) or PVA/PVAC copolymers (PVAC=polyvinyl acetate); andanionic polymers or copolymers based on acrylates (e.g., acrylic binders or latexes).

One application for anti-tack formulations is as a slab dip slurry of relatively low solids content. This is where freshly compounded uncured rubber coming off a two roll mill is run through a dip slurry tank containing the anti-tack formulation in diluted aqueous form to dip coat the rubber slabs. An example of a slab dip use for an anti-tack formulation is shown in U.S. Pat. No. 5,178,676. This patent discloses the use of a surfactant-treated kaolin clay for use as an anti-tack.

U.S. Pat. No. 4,354,001 discloses the use of latex polymers containing carboxylate functionality in combination with fillers as anti-tack composition but there is no teaching of the use of water soluble cationic polymers.

JP 2009 249533 discloses the use of a surfactant and a water soluble polysaccharide polymer (xanthan gum), but there is no mention of the use of a water soluble, cationic polymer nor of talc.

JP 2010 247864 discloses the use of a water soluble PVA polymer for providing an anti-tack film on unvulcanized rubber but does not disclose the use of any water soluble cationic polymers.

WO 2018207939 discloses a typical anti-tack powder product that is dispersed in water at a rubber customer's facility. Anti-tack powders of this kind are typically dispersed on site in water at low solids contents (2-6%) for use as dip slurries for rubber slabs. The inorganic silicates named in this prior art, e.g., component E, does not include talc. Instead, mica and kaolin are listed as the desired material. Also employed in this product is a Na or K fatty acid soap in combination with an organic surfactant.

WO 2017164171 is an example of an anti-tack powder composition that employs a metallic stearate pigment (like Mg stearate or Zn stearate) as an anti-block additive.

JP 2014095010 discloses an anti-tack aqueous dispersion of moderately high solids content, which when calculated has a solids content of about 33.5%. This dispersion utilizes a water soluble polymer in the formulation (e.g., carboxymethyl cellulose and xanthan gum are mentioned), but water soluble cationic polymers are not mentioned. Carboxymethyl cellulose and xanthan gum are carbohydrate-based polymers that are frequently used as rheological thickening agents or as pigment suspension aides.

JP 2013124292 discloses an anti-tack powder composition. This prior art emphasizes the desirability of using inorganic mineral pigments having a low crystalline silica content (for safety purposes with respect to possible inhalation) and it also employs nonionic surfactants (fatty alcohol ethoxylates).

JP 2011144221 discloses an anti-tack powder composition that employs two different classes of nonionic surfactants (fatty alcohol ethoxylates and acetylene-based diol ethoxylates).

JP 2002363532 discloses an anti-tack composition that emphasizes an aqueous dispersion of CaCO3and/or talc in combination with a surfactant package. However, the dispersion is produced at a low solids content, i.e., 7.5% solids based on the amount of water specified in this prior art.

JP 2001348495 discloses an anti-tack composition that employs a water soluble polymer, such as a polyvinyl alcohol, but there is no mention of using a water soluble cationic polymer in combination with talc as an anti-block pigment.

JP 56-47475 discloses an anti-tack composition that can be an aqueous, high solids formulation. However, this formulation is an emulsion derived from a combination of Na oleate soap and an unsaturated fatty acid like oleic acid. There is no disclosure of an aqueous dispersion of a silicate mineral pigment like talc nor is there any teachings concerning the use of a water soluble cationic polymer.

JP 56-47476 discloses an anti-tack composition that can be an aqueous, high solids formulation. However, this formulation is an emulsion derived from a combination of Na oleate soap, a hydroxy-terminated silicone and a fluoro-surfactant. There is no disclosure of an aqueous dispersion of a silicate mineral pigment like talc nor is there any teachings concerning the use of a water soluble cationic polymer.

JP 49-18780 discloses an anti-tack composition that is an aqueous dispersion of a metal stearate anti-block pigment that is wetted with a nonionic or anionic surfactant. The total solids content is about 30% and a silicate mineral pigment such as talc is not used.

ZA 6902507 discloses an anti-tack composition that is an aqueous dispersion that consists principally of a combination of clay mineral, an alkali metal fatty acid soap, and an alkali metal alkyl sulfate surfactant. However, the solids content of the formulation is quite low (about 25%) and the use of talc or a water soluble cationic surfactant is not disclosed.

U.S. Pat. Nos. 6,156,177 and 6,402,827 disclose the formation of cationic polymer flocculated kaolin pigments for use in paper coatings. The preferred water soluble cationic polymer in that application is an Epi-DMA polymer having a Mw<50,000. Neither one of these patents are concerned with anti-tack formulations for use on uncured rubber.

In addition, the use of talc as dry anti-tack powders for dusting elastomeric compounds is well known in the art. The use of talc to produce pellet lube slurries for coating uncured rubber pellets is also well known in the industry. Such pellet lubes are typically spray-applied onto uncured rubber pellets in a rotary drum or alternatively the talc slurry is flooded onto freshly formed, hot pellets as they emerge from a rubber extruder such a Barwell extruder. In these pellet lube applications, the talc-based slurries are typically utilized at a solids content of 10-18% solids. The pellet lube formulations themselves are relatively simple compositions as they are comprised mostly of talc and various alkali metal soaps of fatty acids. One such commercial product is sold by SASCO Chemical/PSG and is called Pellet Lube F3.

Many of the anti-tack dispersions of the prior art suffer from a number of problems that mandate improved dispersions for anti-tack applications. These problems include the requirement that the dry powder products need to be mixed at a customer's site to formulate the dispersion and this requires the customers to have extensive mixing equipment. Other formulations use expensive anti-block pigments like metal stearates. Other formulations suffer from excessive foaming, pigment settling and syneresis, hard and gummy dip slurry sediments that make remixing of the dip slurry dispersion difficult, environmental concerns such as the presence of fibrous asbestiform materials or high levels of total crystalline silica (TCS) in the associated mineral pigmentation, and/or just inferior anti-tack performance.

As such, a need exists to provide improved anti-tack dispersions that avoid or minimize the problem with current anti-tack products and dispersions. The invention responds to this need by providing an improved anti-tack dispersion and method of use in anti-tack applications.

SUMMARY OF THE INVENTION

In one embodiment, the invention relates to an anti-tack formulation that can be conveniently delivered in a high solids liquid concentrate form that can be readily pumped and is easily diluted with water to a lower solids content level for end application use as a dip coating slurry. The desired anti-tack formulation is also relatively low cost as it principally employs cost effective talc pigmentation rather than requiring the use of expensive anti-block pigments such as metal stearates.

Another aspect of the invention is the use of the anti-tack formulation in an anti-tack coating application such as in the spraying of uncured rubber pellets or slab dipping of uncured rubber slabs.

Yet another aspect of the invention is diluted anti-tack formulation that is useful in anti-tack coating applications for uncured rubber compounds whereby the diluted formulation is effective at low solids contents and does not hard pack settle in dip tanks and slurry lines when left non-agitated for extended periods of time.

Other objects and advantages will be become apparent as a further description of the invention is made.

One aspect of the invention relates to an aqueous anti-tack formulation of high total solids content ranging from 45 to 75% by weight of the formulation, preferably 50-75%. The formulation includes talc particles having a Cilas median particle size range of less than 7 microns, the talc particles being present in an amount ranging from 40% to 72% of the total formulation weight.

The anti-tack formulation also includes a polyquaternary cationic polymer having a molecular weight between about 50,000 to 2,000,000 Daltons in an effective amount to at least prevent hard pack settling of the talc when the anti-tack formulation is used in a diluted form for coating uncured rubber compound products and/or improving coating coverage of the uncured rubber compound products.

The Formulation can Also have One or a Combination of the Following:

a) one or more nonionic surfactants of intermediate HLB value of 6 to 12 in a total amount ranging from about 0.01-4.0% of the total formulation weight, preferably up to about 3.0%, and more preferably about 0.5 to 2.0% by weight of the formulation; and b) one or more alkali metal, saturated or unsaturated, C8-C20fatty acid soaps in a total amount ranging from about 0.01-3.0% of the total formulation weight, preferably less than 2.0% by weight of the formulation.

An optional additive to the formulation includes one or more suspension aids in a total amount of not more than about 2.0% by weight of the formulation.

The balance of the aqueous formulation is water.

In a more preferred embodiment, the polyquaternary cationic polymer can be in amount ranging from 0.01 to 0.25% by weight of the formulation, and more preferably less than 0.10% by weight.

In terms of viscosity, the viscosity of the aqueous anti-tack concentrate formulation can be controlled to have one or more of the following viscosities:

an initial 2 rpm static Brookfield Viscosity of 5,000 to 25,000 cps;

a two-week aged 2 rpm static Brookfield Viscosity less than 150,000 cps;

a two-week aged 20 rpm dynamic Brookfield Viscosity less than 25,000;

wherein the initial and aged static and dynamic viscosities are measured using a Brookfield RVDVE heliopath viscometer unit equipped with T-spindles and are run at 2 or 20 rpm and 25 degrees C.

The polyquaternary cationic polymer is preferably epichlorohydrin-dimethylamine (Epi-DMA), one or more polyquaterniums, or a combination thereof and more preferably polydiallyldimethyl ammonium chloride (PolyDADMAC).

The one or more nonionic surfactants can be selected from the group of ethoxylates of alkylphenols, ethoxylates of 2,4,7,9-tetramethyl 5 decyn-4,7-diol, ethoxylates of linear or branched fatty alcohols having a carbon chain length ranging from C6-C18, EO/PO alkoxylates of linear or branched fatty alcohols having a carbon chain length ranging from C6-C18, ethylene oxide/propylene oxide block copolymers, ethoxylates of sorbitan esters, ethoxylated fatty acids, ethoxylated castor oils, ethoxylated fatty amines, and PEG esters or diesters of saturated or unsaturated C8to C20fatty acids. The one or more alkali metal, saturated or unsaturated, C8-C20fatty acid soaps can be selected from sodium or potassium soaps of saturated or unsaturated C8-C20fatty acids.

While only one size tale particle can be used, the talc can be a blend of two differently sized talc particles wherein a size difference between the two differently-sized talc particles is at least two microns, the blend is preferably based on a weight ratio of larger to smaller particles of 1.5:1 to 9:1. The talc can also be substituted with one or more of another anti-block pigment in an amount up to 25% of the total weight of talc in the formulation. The anti-block pigment can be selected from the group consisting of kaolinite, calcined kaolin clays, smectite clay minerals such as bentonite and hectorite, attapulgite, sepiolite, barytes, nepheline syenite, calcium carbonate (ground or precipitated forms), dolomite, fine particle micas consisting of muscovite or phlogopite, feldspars, synthetic amorphous silica pigments such as precipitated silica and fumed silica, alumina trihydrate, hydrotalcite and various metal stearate pigments such as calcium stearate, magnesium stearate and zinc stearate.

Other additives that can be employed in the anti-tack formulation include one or more defoamers in a total amount of not more than about 1.0% of the total formulation weight and one or more biocides in a total amount of not more than about 0.15% by weight of the formulation.

The invention also entails a method of coating an uncured rubber compound to provide anti-tack properties to a surface of the rubber compound by using the inventive high solids anti-tack formulation, diluting it to 1-10% total solids content, preferably 2-6% and more preferably 3-4%, and applying the diluted anti-tack formulation to the rubber compound. The applications can include any type that would coat an uncured rubber compound for anti-tack purposes, and examples include a dip tank slurry application or a spraying application.

A more preferred anti-tack formulation is one that uses at least polydiallyldimethyl ammonium chloride as the polyquaternary cationic polymer, and a combination of both the nonionic surfactant and the one or more alkali metal, saturated or unsaturated, C8-C20fatty acid soaps, with the nonionic surfactant preferably being one or more of ethoxylates of tridecyl alcohol and ethoxylates of 2,4,7,9-tetramethyl 5 decyn-4,7-diol nonionic surfactants and the one or more alkali metal, saturated or unsaturated, C8-C20fatty acid soaps being one or more sodium or potassium soaps of saturated or unsaturated C8-C20fatty acids, and one or more pigment suspension aides of fumed silica, xanthan gum and sepiolite.

Yet another aspect of the invention is providing an aqueous anti-tack formulation comprising the high solids content anti-tack formulation described above in diluted form such that the total solid content ranges from about 1 to 0%. This formulation can also have the same aspects of the high solids formulation in terms of different talc particle sizes, the substitution of talc with one or more anti-block pigments, presence of optional additives, and the like. For the diluted anti-tack formulation, it is preferred that it has a relative sediment volume (RSV) of at least 35 cm3, the relative sediment volume measured using 1000 ml of a 4% solids diluted form of the anti-tack slurry formulation in a 1 liter graduated cylinder after 24 hours of static settling.

A further aspect of the invention is a method of making the aqueous anti-tack formulation having a total solids content ranging from 45-75%. This method includes adding a number of components together to make the anti-tack formulation. More particularly, the adding step adds an amount of at least one size of fine particle size talc, an amount of one or more polyquaternary cationic polymers, an amount of either or both of: (i) one or more nonionic surfactants of intermediate HLB value of 6 to 12; and (ii) one or more alkali metal, saturated or unsaturated, C8-C20fatty acid soaps, an optional amount of one or more suspension aids, defoamers, and biocides, and water to form the aqueous anti-tack formulation. When adding these various components together, the amount of the one or more polyquaternary cationic polymers is made into an aqueous solution and this aqueous solution is used when making the anti-tack formulation by adding the other components together.

