Background of the Invention

The invention relates to a method of lubricating a tire during manufacture thereof by foaming a coemulsion of amino functional silicone fluid and oxidized polyethylene homopolymer thereon.

Automobile rubber tires are produced by molding and curing green tires in a molding press wherein an internal fiuid expanded bladder outwardly presses the green tire to the die surface. The green tire is then molded to receive the tread pattern and side wall pattern of the die surface. During the manufacturing process, the curing bladder has a tendency to adhere to the uncured tire carcass which hinders production and may damage both the curing bladder and the tire carcass. Additionally, air bubbles may potentially be trapped between the curing bladder and the inner tire surface and promote tire vulcanization defects. For this reason, it is common to coat the inner tire surface with a lubricant in order to provide lubricity between the outer bladder surface and the inner tire surface.

U.S. Patent 4,889,677 discloses that a releasing agent such as one composed of a silicon emulsion has been used on conventional curing bladders in order to improve the lubrication with the inner tire surface. However, this releasing agent is undesirable because although the releasabilitγ between the bladder surface and the inner tire surface is improved, the bladder surface durability is decreased which makes it unsuitable for practical use.

Band fly lubricant, which is based on predominately polydimethylsiloxane oils, has also been used on conventional curing

bladders in order to improve the lubrication with the inner tire surface. Band fly lubricant is disadvantageous to use because it is manually brushed on every inner tire surface before the curing bladder is inserted into the tire. Thus, this lubrication method is time consuming because it is labor intensive.

Tire manufacturers are constantly seeking ways to reduce their manufacturing cycle time. It would be desirable to have a lubrication method which reduces lubrication time and cost.

Summary of the Invention

We have found a lubricant and lubricating method which responds to the foregoing need in the art. Thus, the present invention provides a manufacturing assembly comprising: (a) a rubber product; (b) a curing bladder; and (c) a lubricant which is located between the rubber product (a) and the curing bladder (b), is present in an amount sufficient to provide lubrication between the rubber product (a) and the curing bladder (b), and comprises a coemulsion of: (i) at least one oxidized polyethylene; and (ii) at least one amino functional silicone. The present lubricant is advantageous to use because the release properties of the currently used dimethylsiloxane oil are achieved by the use of significantly lower amounts of silicone lubricants (approximately one fifth of the level) due to the synergy which occurs between the oxidized polyethylene and the amino functional silicone oil. Also, the present lubricant adheres better to the rubber product and the curing bladder.

The present invention also provides a method of making a rubber product comprising the steps of: (a) foaming a coemulsion on the inner surface of an unvulcanized rubber product wherein the coemulsion is present in an amount sufficient to lubricate the surface and comprises: (i) at least one oxidized polyethylene; and (ii) at least one amino functional silicone; (b) placing a curing bladder inside the unvulcanized rubber product; (c) placing the unvulcanized rubber

product and the curing bladder in a mold; (d) pressurizing the curing bladder into contact with the inner surface of the unvulcanized rubber product to conform the unvulcanized rubber product to the internal surface of the mold; and (e) applying heat to cure the unvulcanized rubber product to form a vulcanized rubber product having a shape determined by the mold. This lubrication method is advantageous because it reduces the time currently spent on lubrication.

Other advantages of the present invention will be apparent from the following description and attached claims.

Description of the Preferred Embodiments

Any conventional rubber tire carcass may be used in the present invention.

Any conventional curing bladder may be used in the present invention. Generally, curing bladders are made of elastomer. Examples of useful elastomers include those made from conjugated dienes which have 4 to 8 carbon atoms such as butadiene and isoprene and include both natural and synthetic rubbers. Other useful elastomers are various copolymers made from one of the foregoing conjugated dienes and a vinyl substituted aromatic having 8 to 12 carbon atoms such as styrene and alpha-methyl styrene. An example of a specific copolymer is styrene-butadiene rubber. Other useful curing bladder materials include various polyurethanes which are reinforced with polyamide cords.

The present coemuisions are disclosed in commonly assigned U.S. Patent 5,238,731 to Blanch et al. which is incorporated herein by reference. The coemulsion is used in an amount sufficient to provide lubrication between the rubber product and the curing bladder. Typically, the amount of coemulsion is about 10 to about 20 grams dry weight to 1 5 inch "G ⁿ or "H" series tire. The amount of coemulsion is preferably about 12 to about 16 grams dry weight to 15

inch "G" or "H" series tire. The coemulsion is typically applied to the inner tire surface.

Suitable polyethylenes for the coemulsion may be characterized as oxidized low density and high density homopolymers of ethylene; copolymers containing acrylates and ethylene; and terpolymers containing acrylates, esters, and ethylene. These polyethylenes have preferably been oxidized to an acid number as determined by a standardized titration of KOH of about 5 and about 55, more preferably between about 10 and about 50, and most preferably between about 10 and about 45. These polyethylenes typically have a density as determined by ASTM D-1 505 in the range of about 0.85 to about 1 .05, more preferably in the range of about 0.87 to about 1 .05, and most preferably, in the range of about 0.90 to about 1 .00. Preferably, these oxidized polyethylenes exhibit a Brookfield viscosity at a temperature of 140 degrees C of between about 185 and about 6000 centipoises, more preferably in the range of about 190 and about 6000 centipoises, and most preferably in the range of between about 190 and about 5500 centipoises.

Suitable oxidized polyethylenes are available from AlliedSignal Inc., Morristown, New Jersey. Preferred oxidized polyethylenes are listed in the following Table:

The more preferred polyethylenes are A-C ^® 325 polyethylene, A-C ^® 330 polyethylene, A-C ^® 629 polyethylene, and A-C ^® 680

polyethylene. The most preferred polyethylenes are A-C® 325 polyethylene and A-C ^® 629 polyethylene.

These oxidized polyethylenes as well as others which are useful in the practice of the instant invention may be obtained by oxidizing polyethylenes with air or oxygen by conventional procedures. Suitable methods are described in U.S. Patents 3,060, 1 63 and 3,322,71 1 , which are incorporated herein by reference. As those skilled in the art know, the oxidation results in the scission of the polymer and the formation of acid groups. In addition to the formation of acid groups on the polymer chain, esters, aldehydes, ketones, hydroxides, and peroxides are also found in various quantities along the polymer chains.

Appropriate amino functional silicone fluids which may be used in accordance with the invention are those which may be broadly described as amino organic modified polysiloxanes, alternatively known to the art as "polydiorganosiloxanes". Preferable polydiorganosiloxanes include those which include the characteristic of exhibiting an amine neutral equivalent in the range of approximately between about 1000 and about 3000, more preferably in the range of between about 1200 and about 3000, and most preferably in the range of between about 1250 and about 2800. Examples of commercially available polydiorganosiloxanes which find use in the instant invention include those which are marketed under various trade designations. One suitable group of materials include Dow Corning ^® CSF and Dow Corning ^® SSF which are sold as lubricating compositions. These materials are described as medium viscosity polydiorganosiloxane which comprise aminoalkyl groups affixed to a predominantly polydimethylsiloxane structure. The amine neutral equivalent is described to be approximately 2000, the specific gravity at 25 degrees C (77 deg.F) of 0.96, and to have a viscosity at 25 degrees C (77 deg.F) of 1300 centistokes. A further commercially available material includes UCARSIL ^® Magnasoft™ materials available from Union Carbide Corporation. These materials are described to be low viscosity amino functional silicones which have a viscosity of

about 250 centistokes at a temperature of 25 degrees C (77 deg.F) and a specific gravity of 0.97 at 25 degrees C (77 deg.F). A further commercially available polydiorganosiloxane material includes those which are marketed by PPG-Mazer under the designations MASIL ^® 1 23 and MASIL ^® 1 24.

As had been noted, the microemulsion includes at least one constituent selected from the group consisting of; ethoxylated aliphatic amines, ethoxylated octylphenols, ethoxylated nonylphenols, ethoxylated primary alcohols, and ethoxylated secondary alcohols. The at least one constituent selected from this group which is added to the polyethylene and the amino functional silicone fluid in accordance with the teaching of this present invention may be interchangeably referred to as the "additive system", and it is to be understood that the "additive system" includes only one or more of constituents selected from: ethoxylated aliphatic amines, ethoxylated octylphenols, ethoxylated nonylphenols, ethoxylated primary alcohols, and ethoxylated secondary alcohols. It is further to be understood that while further composition, constituents, reagents and the like might find use in conjunction with the present invention, and which might be known to the art as useful additives, the term "additive system" as used throughout this specification and the claims are to be understood to be limited to the group of four constituents described.

The ethoxylated aliphatic amines which are suitable to the practice of the invention are those which may be described as saturated and unsaturated fatty amines reacted with ethylene oxide. These materials which are useful in the practice of the present invention may be generally termed as the condensation products of ethylene oxide with a hydrophobic material such as a long chain aliphatic alcohol, ester, acid, ether, or alkyl phenol. These materials which find use in conjunction with the invention are characterized by containing as the hydrophilic portion of the molecule a plurality of oxyethylene moieties. Suitable materials of this type may also be referred to as ethoxylated tallow amines, a designation commonly used in the art.

Examples of preferred ethoxylated aliphatic amines which are presently commercially available include "Ethomeen T-1 2" and "Ethomeen 1 8/12" which is available from Akzo Chemie America and which is described as an ethoxylated tallowamine, more particularly described as bis-(2-hydroxyethyl) tallowamine. A further example includes "Varonic T-202" which may be described as a constituent having similar characteristics to those described in conjunction with Ethomeen T-1 2 above, and are believed to be functionally identical. Varonic T-202 is at present commercially available from the Sherex Co., Chicago III. Further preferred ethoxylated surfactants include ethoxylated octylphenols and nonylphenols which may be described as being the reaction products of an octylphenol or a nonylphenol with ethylene oxide. Examples of preferred ethoxylated octylphenols and nonylphenols which find use with the instant invention include those which are sold under the designation "Igepal CO-430" which is sold as a surfactant and available from Rhone Poulenc Corporation and which is described as an ethylene oxide, more particularly as nonylphenoxypoly(ethyleneoxy)ethanol having a molecular weight of 484, and a boiling point in excess of 93.30 degrees C.

Preferred ethoxylated alcohols include ethoxylated primary alcohols and ethoxylated secondary alcohols suitable in the practice of the present invention include those which may be described as the reaction product of a primary alcohol or a secondary alcohol and ethylene oxide. Examples of such commercially available ethoxylated alcohols include; "Tergitol 15-S-3" available from Union Carbide Corp. of Danbury, Connecticut which is described as an ethoxylated secondary alcohol, "ETHAL TDA-3" from Ethox Chemical Co. of Greenville, South Carolina, which is described as an ethoxylated tridecyl alcohol formed as the reaction product between stoichiometric quantities of 3 moles of ethylene oxide with one mole of tridecyl alcohol, or Neodol 25-3 which is commercially available from Shell Chemical Co. of Houston, Texas.

According to the invention, the polyethylene and amino functional silicone fluid further includes the additive system which consists of at least one constituent selected from among the group consisting of: ethoxylated aliphatic amines, ethoxylated octylphenols, ethoxylated nonylphenols, ethoxylated primary alcohols, and ethoxylated secondary alcohols. Where the additive system consists of only one constituent, then it is to be recognized that the selected constituent forms 100 percent of the additive system's composition. It is preferred however that the additive system comprise at least two components where one component is an ethoxylated aliphatic amine, and the other component or components are selected from the remaining members of the group, namely the ethoxylated octylphenols or nonylphenols, ethoxylated primary alcohols, and ethoxylated secondary alcohols. More preferably, the composition of the additive system consists of the following constituents in the following proportions: ethoxylated aliphatic amines in 40 - 100 % mol., ethoxylated nonylphenol in 0 - 60 % mol., ethoxylated primary alcohols in 0 - 60 % mol., and ethoxylated secondary alcohols in 0 - 60 % mol. Most preferably, the relative molar percentages of the constituents making up the additive system are present in the following ratios: ethoxylated aliphatic amines in 60 - 100 % mol., ethoxylated nonylphenol in 0 - 40 % mol., ethoxylated primary alcohols in 0 - 40 % mol., and ethoxylated secondary alcohols in 0 - 40 % mol.

Additional constituents may be incorporated in the inventive compositions, and such constituents may be in any amount which does not detract from the benefits of the invention.

Water may be present in any quantity which does not have any detrimental effect upon the formation of the emulsion according to the teachings of the invention. Preferably, quantities of between about 30 to about 90 percent by weight of the total composition, more preferably between about 45 to about 90 percent by weight, most preferably between about 60 to 80 percent by weight of water are included in the total composition.

A further constituent which may be used in formulating microemulsion compositions includes acetic acid in either glacial or dilute forms, which may be added in order to modify the relative acidity of the composition by adjusting the respective pH value thereof. Preferably, the pH should be maintained to adjust the relative affinity to the ethoxylated amine so that material exhibits a greater affinity to the olefins in the overall composition rather than an affinity to any water contained in the overall composition.

Hydrochloric acid, in either concentrated, i.e. approximately 37% concentrations, or dilute concentrations, i.e., 1 2% or less, may also be included in formulating the inventive compositions. When added, hydrochloric acid functions to provide a means to adjust the relative pH of the overall compositions as is described above.

Ammonium hydroxide is a further useful reagent which may be included in the composition and preferably, concentrated ammonium hydroxide of an approximate 30% concentration may be used. It has been observed that the presence of ammonia, in even minor amounts in microemulsion compositions according to the present invention, imparts a beneficial effect upon the composition which is evidenced by reductions in the opacity of the microemulsions formed containing ammonia relative to the opacity of the microemulsions formed without containing ammonia. This is evident from the improved appearance and measured light transmission measurements which are factors known to the art to be indicative of the relative particle size in an emulsion.

Sodium salts, including but not limited to sodium chloride, sodium hydroxide, and sodium metabisulfite may be incorporated as a constituent, as the salt provides the desirable effect of reducing the viscosity, and where the salt is sodium metabisulfite, to improve the color and optical characteristics of the composition. The sodium salts may be in any form, such as a finely divided powder, or in a pelletized form, or alternately, the sodium salt may be dissolved in a reagent or

other constituent, for example in the water comprising a composition which is subsequently combined with the other constituents. The salts may also be in various percentages, and may further include small amounts, i.e., 20 % or less of inert materials which exhibit no detrimental effect upon the practice of the invention.

It is recognized and understood that although only particular constituents have been recited above, other materials which are known to the art which find use in the compositions of emulsions may be included, and such additives are considered as part of the invention disclosed herein.

The process for forming the microemulsions of the present invention includes the following process steps: heating the constituents used to form the microemulsion under conditions of constant agitation in a sealed and pressurized reaction vessel through the melt point of the oxidized polyethylene constituent, further raising the temperature of the constituents beyond the melt point of the oxidized polyethylene constituent to a maximum temperature, maintaining the constituents at this maximum temperature for a first residence time interval, and then cooling the constituents. In an altemative embodiment of the process, the heating of the constituents comprises two heating steps; applying heat at a first heating rate to a first intermediate temperature and then heating the constituents from the first intermediate temperature to the maximum temperature at a second heating rate. Preferably, the first heating rate is greater than the second heating rate, i.e., a faster transmission of heat per unit of time occurs during the first heating rate than during the second.

Any suitable vessel capable of withstanding the operating parameters of the process may be used in conjunction with the present invention. By way of example, suitable reactors include those constructed of metals, glass, and glass-lined metals. Preferably, the reaction vessel is a batch type reaction vessel which may be sealed, and which is of sufficient strength so to withstand the pressure

generated by the constituents during the process of forming the microemulsion.

It is contemplated that the reaction may be carried out in any manner, either in a batch type mode, or in a continuous mode or other mode of operation; any reaction mode which is successful in providing the conditions for the productions of the emulsions taught herein may be utilized. Preferably, the reaction is carried out in a batch type mode.

Agitation means are meant to include any means, or alternately any method by which the constituents in the reactor may be well mixed, and by way of example, such means include rotary paddles, propellers, stirring rods, vanes and the like, as well as other methods which may comprise shaking, spinning, or otherwise effecting movement of constituents within the reactor. In a preferred embodiment of the process, the selected constituents comprising an oxidized polyethylene, amino functional silicone fluid, and the additive system as defined above, as well as other desired constituents are loaded into a reaction vessel which is sealed, and which includes agitation means. The selected constituents are heated, with agitation, at a first heating rate through the melting point of the oxidized polyethylene component for a first time interval, and then during a second time interval further heated at a second heating rate to raise the temperature to a maximum temperature or maximum temperature range approximately 7-10 deg.C beyond the melt point of the oxidized polyethylene component, and then maintaining the reactants at this maximum elevated temperature or maximum temperature range for a period of between about 10-15 minutes. After the period had elapsed, the materials were then cooled to room temperature. Agitation is maintained throughout the procedure.

The order of adding or combining the constituents is not critical, and they may be added in any order as is suitable for use with the reactor and the reaction method employed.

The relative acidity of the composition, i.e., the "pH" should be evaluated in order assure that the microemulsion is of suitable optical clarity. Preferably, the pH may be adjusted by modifying the amounts of the constituents used, especially by modifying the amount of acetic acid and/or hydrochloric acid used. Preferably, the pH of the microemulsion should be maintained in a range of between about 4 to about 6, more preferably in the range of between about 4.5 and about 5.5, and most preferably in the range of between about 4.75 and about 5.25.

The coemulsification products of this procedure form stable coemulsions of the oxidized polyethylene and amino functional silicone fluid, which include particles in the size range of between about 0.0001 and about 100 microns. Preferably, the products of this procedure have particle sizes in the range of between about 0.001 and about 5 microns, and most preferably comprise particles having particle sizes in the range of about 0.001 and about 1 micron. The small particle sizes of the present invention are generally classed as characteristic of a "microemulsion". As is well known in the art, the smaller particle sizes of the emulsion enhance the distribution of the silicon in the emulsions, and improve the distribution of the silicon within or upon the surface of any material and thereby impart such desirable properties as lubrication with a consequent reduction in the amount of silicon or other constituent required to form a suitable coemulsion.

To practice the present method of making a rubber product, the above coemulsion is foamed on the inner surface of an unvulcanized rubber product wherein the coemulsion is present in an amount sufficient to lubricate the surface. Any conventional foaming means such as a chemical foam system manufactured by Gaston County Dyeing Machine Company, Stanley, North Carolina may be used. A curing bladder is then placed inside the lubricated unvulcanized rubber product. The unvulcanized rubber product and curing bladder are placed in a mold. The curing bladder is then pressurized into contact with the inner surface of the unvulcanized rubber product to conform

the unvulcanized rubber product to the internal surface of the mold. Heat is then applied to cure the unvulcanized rubber product to form a vulcanized rubber product having a shape determined by the mold.

The present invention is more fully illustrated by the following non-limiting Examples.

EXAMPLES

In the Examples, the following oxidized polyethylenes are used in the lubricants:

Dow Corning® CSF is polydiorganosiloxane. Ethomeen 18/12 and Ethomeen T- 12 are bis-(2-hydroxyethyl) tallowamine. Igepal CO-430 is a surfactant. For each Example, a stainless steel reactor having a capacity of 2 liters and equipped with an electrical resistance-type heating system in the form of coils which was placeable near the exterior of the reactor and a stirrer attached to a variable speed electric motor, as well as a thermometer, is used. This stainless steel reactor is emptied and thoroughly cleaned before the formulation and production of each Example. All components are in units of grams.

Each coemulsion listed in the Table below is applied to an unvulcanized rubber product by foaming a coemulsion on the inner surface of the unvulcanized rubber product. A curing bladder is then placed inside the lubricated unvulcanized rubber product. The unvulcanized rubber product and curing bladder are placed in a mold. The curing bladder is pressurized into contact with the inner surface of the unvulcanized rubber product to conform the unvulcanized rubber product to the internal surface of the mold. Heat is then

applied to cure the unvulcanized rubber product to form a vulcanized rubber product having a shape determined by the mold. In each Example, the curing bladder is readily removed from the vulcanized rubber product because the lubricant is present.

COMP. EX.1 EX.2 EX.3 EX.4 EX.5. EX.6 EX.7

A-CΘ629 128 128 128 128

A-C®325 ... 128 128 128

Dow CSF 32 32 32 32 32 32 32

Ethomeen ... — — 51.2 18/12

Ethomeen 56.8 56.8 56.8 56.8 51.2 51.2 T-12

Igepal 14.2 14.2 14.2 14.2 12.8 12.8 12.8 CO-430

Glacial Acetic 8 7.4 6.4 6.7 7.5 7 6.5 Acid

Hydrochloric ... 5 ... — Acid, 10%

Hydrochloric ... ... 5.4 — — Acid, 37%

NH 0H, ... ... 0.2 0.2 0.2 30%

NaCl 0.5 0.5 0.5 ...

NaOH ... ... 0.3 ... ... ...

Na-jS->Oκ ... ... 0.75 0.5 0.25 0.25

KOH ... ... ... ...

Water 514.4 514.4 514.4 514.4 514.4 515 515