KR20080063823A - Thermoplastic polyurethane powder compositions and uses - Google Patents

Abstract

Thermoplastic powder compositions and related processes of the invention comprise at least one thermoplastic polyurethane having a melt flow index of at least about 8 g/10 min when tested according to ASTM D1238 at 190 °C and a weight of 2.16 kg; at least one internal lubricant in an amount of up to about 5 weight % based on total weight of the composition; and, optionally, at least one flow agent or other components. Such thermoplastic powder compositions are suitable for formation into a variety of articles using, for example, high velocity impact fusion or slush molding techniques.

Description

Thermoplastic Polyurethane Powder Compositions and Uses {THERMOPLASTIC POLYURETHANE POWDER COMPOSITIONS AND USES}

The present invention relates to thermoplastic polyurethane powder compositions and uses thereof.

Over the past decades, the use of polymers has changed the world. Polymer science has rapidly developed to produce thousands of different thermoplastic and thermoset products within the following four polymer classes: thermoplastics, thermoplastic elastomers, thermoset plastics and thermoset elastomers.

Large scale production of any polymer or article therefrom may not depend on current components or processing conditions. Lower costs, improved productivity, better delivery of deliveries, and lower cost products all lead the polymer science industry. Due to the emergence of new materials and related methods, it is often beneficial to replace old polymeric materials with materials having improved features, processing capabilities and / or processing efficiencies in certain applications and related methods.

For example, in certain applications, replacement of polyvinyl chloride (PVC) is desired. Articles formed from relatively inexpensive and easy to process PVC are brittle when used at lower temperatures (thus exhibiting a brittle failure mode). Thus, using PVC to form cold weather and other relatively low temperature exposed articles can be problematic for certain applications requiring a ductile failure mode.

In particular, one use where a soft failure mode is desired includes the manufacture of articles for passenger compartments of vehicles such as automobiles, aircraft, trucks, farm equipment, construction equipment and the like. Polymeric materials are used to make various parts and subassemblies in the passenger compartment described above. For example, instrument panels, door panels, armrests, headrests, center consoles and airbags can be made from one or more polymeric materials.

Sub-components of such articles often take the form of polymeric skins. The polymer skin can be filled with molded foam or other cushioning material to provide an outer surface of the larger article that provides a sculpted appearance throughout the body and the article. For example, padded or cushioned articles in a passenger compartment, such as instrument panels, door panels, etc., have been made by providing a powdered PVC slush molded skin. The skin is held in place on the substrate and then refilled with a foam (eg urethane foam) material in an injection process where the edges of the skin are sealed to provide the final product. The final product includes a skin with padded foam backing coupled to the substrate, which may include the edge of the door panel, the edge of the instrument panel, and the like. References to the use of polymer skins in this manner can be found, for example, in US Patent Publication No. US 2002/0125734 A1.

However, where materials exhibiting brittle fracture modes at some or all temperatures of their intended use are used to make polymer skins for such uses, they expose passengers to danger upon impact or in other situations that result in the destruction of the article. Let's do it. This risk is increased by using brittle materials due to the tendency of brittle materials to shatter upon breakdown and to break down into many small pieces, often with jagged or sharp edges. The formation of such debris threatens their safety inside and outside the passenger compartment.

As such, the prerequisites in selecting a material for use in the manufacture of a vehicle often include testing to determine whether the material is suitable for use in a variety of environments. In particular, the material for one article-the airbag-in the passenger compartment is carefully selected under various environmental conditions. The performance of materials at temperatures of about −40 ° C. (-40 ° F.) and below is an important threshold to be considered in determining the ability of materials to pass these tests. PVC often fails the above test because of its tendency to brittle at lower operating temperatures. Nevertheless, PVC is advantageous over conventional alternatives because of its relatively low cost. Thus, alternative materials are desired.

Not only are additional materials desired, but also efficient and repeatable methods of making articles from such materials are also desired. Various processes are known for producing polymeric parts, such as those described above. One specific process for forming the polymer skin is referred to as high velocity impact fusion (HVIF). In this process, the polymer powder is fluidized and melted in an inert gas such as nitrogen and then accelerated into a mold or other apparatus where the powder accumulates on one or more target surfaces and then solidifies into a continuous film. Typically, the target surface described above is maintained at approximately room temperature to promote membrane coagulation. See, for example, US Pat. No. 5,285,967.

HVIF has been used to provide a polymeric coating onto an article to protect the material or the underlying surface from contacting the underlying surface from damage (eg, contamination). Often, polymeric coatings provide a relatively clean, non-toxic surface and are made of a relatively inert material. For example, polyethylene is coated on the interior of a steel railroad car using HVIF to prevent contamination of food products carried by the railroad car.

Due to the processing advantages associated with the method and its ability to form articles with desired surface properties, it is desirable to expand the application of HVIF to additional materials. This applies in particular to those uses requiring a surface finish of a certain diameter (eg, having a smooth and uniform appearance, or having a uniform leathery appearance). However, to date, expanding HVIF to include the manufacture of industrial articles, such as those involving the manufacture of polymeric articles used in passenger compartments, is a reason why powder compositions suitable for this specific process have not yet been known. It was difficult. As such, injection molding is a viable method of forming polymeric skins and other polymeric articles in these applications because of the limitations and disadvantages associated with HVIF, and other manufacturing techniques (eg, vacuum forming, slush molding, rotational molding and spraying). It has been. See also US Patent Publication No. US 2002/0125734 A1.

Summary of the Invention

Advantageously, the present invention provides a thermoplastic powder composition suitable for forming into an article using high speed impact melting. Such powder compositions have a uni-modal particle size distribution and at least one having a melt flow index of at least about 8 g / 10 minutes when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg. Thermoplastic polyurethanes; One or more internal lubricants present in an amount of about 5% by weight or less based on the total weight of the composition; And optionally one or more glidants or other components (eg, heat stabilizers, light stabilizers, pigments, antioxidants, plasticizers, fillers and matting agents).

Other thermoplastic powder compositions are also possible with the present invention. Depending on the application, the powder composition may have a unimodal or bi-modal particle size distribution.

For example, the present invention provides thermoplastic powder compositions suitable for forming into articles using slush molding. Such powder compositions have a bimodal particle size distribution and at least one thermoplastic polyurethane having a melt flow index of at least about 8 g / 10 minutes when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg; One or more internal lubricants present in an amount of about 5% by weight or less based on the total weight of the composition; And optionally one or more glidants or other components (eg, heat stabilizers, light stabilizers, pigments, antioxidants, plasticizers, fillers and deglossants).

In an exemplary embodiment of the invention, the thermoplastic polyurethane comprises an aliphatic thermoplastic polyurethane or an aromatic thermoplastic polyurethane. In a further embodiment, the thermoplastic polyurethane is a polyether based thermoplastic polyurethane (eg, an aromatic polyether based thermoplastic polyurethane) or a polyester based thermoplastic polyurethane (eg, an aliphatic polyester based thermoplastic). Polyurethane).

Although the amount of individual components may vary depending on the desired application and process, in one embodiment the thermoplastic powder composition comprises from 0.01 to about 1.0 weight percent of internal lubricants such as mono- and di-stearyl acid phosphates. do. Preferably, but not necessarily, the composition is essentially free of blooming mobile ingredients in articles made from the composition.

In further embodiments, the powder composition may be a blend of powder compositions. Powder composition formulations of the present invention comprise one or more thermoplastic polyurethanes and one or more other polymers (eg, polyvinyl chloride). In one exemplary embodiment, the other polymer is included in more than about 10% by weight of the total composition. For example, the other polymer may be polyvinyl chloride included in an amount up to about 90% by weight of the total composition. In an exemplary embodiment of a powder composition formulation, the composition comprises about to about 50 weight percent, about 10 to about 30 weight percent, or even further about 15 to about 25 weight percent thermoplastic polyurethane based on the total weight of the composition It includes. Other components may also be present, including, for example, melt processible rubber.

Various articles can be made from the thermoplastic powder compositions of the present invention. For example, in a further article for the passenger compartment of the vehicle, subcomponents of the polymer skin can be formed from the thermoplastic powder composition of the present invention. Such additional articles include instrument panels, door panels, armrests, headrests, center consoles, and airbags for the passenger compartment of the vehicle. The compositions of the present invention advantageously provide advantages over the conventional materials used for such uses, and alternatives to such conventional materials.

The method of the present invention includes a method of preparing a thermoplastic powder composition. The methods described above include providing a thermoplastic polyurethane, mixing the thermoplastic polyurethane with one or more optional components, and transforming the thermoplastic polyurethane and the optional components into a unimodal or powder having a predetermined particle size distribution. In one exemplary embodiment, the composition is transformed into a powder using cryogenic polishing, screening and recycling steps.

Methods of making articles from thermoplastic powder compositions include those using high speed impact melting, fluidized bed powder coating, electrostatic spraying, thermal spraying, slush molding, or rotational molding techniques. According to an exemplary embodiment of the present invention, an external mold release agent is used to form the article described above, but this is not essential.

Composition

The thermoplastic polyurethane (TPU) powder composition of the present invention comprises at least one base TPU selected from the composition, and at least one optional component, depending on the intended use of the composition.

Base TPU

TPUs are preferred thermoplastic elastomers that exhibit high tensile and tear strength, high flexibility at low temperatures, and very good wear and scratch resistance. TPUs are also relatively stable against far ultraviolet radiation as well as oils, lipids and many solvents. Because of these desirable properties, TPU can be advantageously used for many end use applications, including the automotive and footwear industries.

In short, as used herein, the term "polyurethane" refers to a polymer containing urethane (also known as carbamate) bonds, urea bonds, or combinations thereof (ie, in the case of poly (urethane-urea)) It includes. Accordingly, the thermoplastic polyurethanes of the present invention contain one or more urethane bonds, and optionally urea bonds.

A wide range of TPU chemistries are suitable for use as the base TPU in the present invention. For example, the chemistry of many aliphatic and aromatics can be used. One or more TPU chemistries may be used to form the base TPU for the compositions of the present invention.

The term "aromatic" refers to a TPU derived from a mononuclear aromatic hydrocarbon group or a polynuclear aromatic hydrocarbon group. This term includes TPUs derived from arylene groups. The term "arylene group" means a divalent aromatic group.

The term "aliphatic" refers to a TPU derived from linear, branched or cyclic hydrocarbon groups, saturated or unsaturated. This term is used to include such TPUs derived from, for example, alkylene (eg oxyalkylene), aralkylene and cycloalkylene (eg oxycycloalkylene) groups. The term "alkylene group" means a saturated, linear or branched divalent hydrocarbon group. Particularly preferred alkylene groups are oxyalkylene groups. The term "oxyalkylene group" means a saturated, linear or branched divalent hydrocarbon group having a terminal oxygen atom. The term “aralkylene group” means a saturated, linear or branched divalent hydrocarbon group containing one or more aromatic groups. The term "cycloalkylene group" means a saturated, linear or branched divalent hydrocarbon group containing one or more cyclic groups. The term "oxycycloalkylene group" means a saturated, linear or branched divalent hydrocarbon group containing one or more cyclic groups and terminal oxygen atoms.

According to one embodiment of the present invention, the TPU comprises a bifunctional isocyanate composition comprising at least one difunctional polyhydroxy compound and optionally a chain extender and an isocyanate index of about 90 to about 110, preferably about 95 to about 105 And, most preferably, by reacting at such an amount to bring about 98 to about 102.

As used herein, the term "bifunctional" means that the average functionality of the isocyanate composition and the polyhydroxy compound is about 2.

As used herein, the term “isocyanate index” is the ratio of isocyanate groups to isocyanate reactive hydrogen atoms present in the composition, given as a percentage. That is, the isocyanate index represents the percentage of isocyanate actually used in the composition relative to the amount of isocyanate theoretically needed to react with the amount of isocyanate reactive hydrogen used in the composition. As used herein, the isocyanate index is considered in terms of the actual polymer formation process comprising the isocyanate component and the isocyanate-reactive component. Isocyanate groups to produce any isocyanate groups consumed in a preliminary step to produce modified polyisocyanates (including those isocyanate derivatives known in the art as quasi- or semi-prepolymers), or modified polyols or polyamines. Any active hydrogen reacted does not take into account the calculation of the isocyanate index. Only the free isocyanate reactive hydrogen and free isocyanate groups present in the actual elastomer formation step are considered.

In this embodiment, the bifunctional polyhydroxy compound has a weight average molecular weight of about 500 to about 20,000, which compound is a diol such as polyesteramide, polythioether, polycarbonate, polyacetal, polyolefin, polysiloxane, poly Butadiene and, preferably, polyesters and polyethers, and mixtures thereof. Other dihydroxy compounds such as hydroxy terminated styrene block copolymers such as known SBS, SIS, SEBS, or SIBS block copolymers can also be used.

Mixtures of two or more compounds of such or other functionalities, and in proportions such that the average functionality of the entire composition is about 2, can also be used as bifunctional polyhydroxy compounds. For polyhydroxy compounds, the actual functionality may be less than the average functionality of the initiator, somewhat due to some terminal unsaturation. Thus, for example, small amounts of trifunctional polyhydroxy compounds may also be present to achieve the desired average functionality of the composition.

Polyether diols that may be used include products obtained by the polymerization of cyclic oxides, such as ethylene oxide, propylene oxide, butylene oxide or tetrahydrofuran, in the presence of a bifunctional initiator, if desired. Suitable initiator compounds contain two active hydrogen atoms, including water; Butanediol; Ethylene glycol; Propylene glycol; Diethylene glycol; Triethylene glycol; Dipropylene glycol; 1,3-propane diol; Neopentyl glycol; 1,4-butanediol; 1,5-pentanediol; 1,6-pentanediol; Etc. are included. Mixtures of initiators and / or cyclic oxides can be used.

Particularly useful polyether diols include polyoxypropylene diols and poly (oxyethylene-oxypropylene) diols obtained by simultaneous or continuous addition of ethylene or propylene oxide to a bifunctional initiator. Random copolymers having an oxyethylene content of about 10 to 80 weight percent, block copolymers having an oxyethylene content of up to about 25 weight percent, and up to about 50 weight percent oxyethylene based on the total weight of the oxyalkylene units Mention may be made of random / block copolymers having a content, in particular copolymers having at least some oxyethylene groups at the ends of the polymer chains. Other useful polyether diols include polytetramethylene diols obtained by the polymerization of tetrahydrofuran. Polyether diols containing low levels of unsaturation (ie, less than about 0.1 milliequivalents per gram of diol) are suitable.

Other diols include dispersions or solutions of addition or condensation polymers in diols of the type described above. Such modified diols, often also referred to as “polymeric diols”, are obtained by in-situ polymerization of one or more vinyl monomers such as styrene and acrylonitrile in polymeric diols such as polyether diols, or in polymer diols. Included are products obtained by in situ reaction of polyisocyanates with amino- and / or hydroxyfunctional compounds such as triethanolamine.

Also useful are polyoxyalkylene diols containing about 5 to 50 weight percent dispersed polymer. Particle sizes of dispersed polymers of less than 50 microns are preferred.

Polyester diols that may be used include dihydric alcohols such as ethylene glycol; Propylene glycol; Diethylene glycol; 1,4-butanediol; Neopentyl glycol; 2-methylpropanediol; 3-methylpentane-1,5-diol; 1,6-hexanediol; Cyclohexane dimethanol; And mixtures of such dihydric alcohols with divalent carboxylic acids or ester forming derivatives thereof (eg, succinic acid, glutaric acid and adipic acid, or dimethyl esters, sebacic acid, phthalic anhydride, tetrachlorophthalic anhydride, Hydroxyl-terminated reaction products of dimethyl terephthalate and mixtures thereof).

Polyesteramides can be obtained by containing aminoalcohols such as ethanolamine in the polyesterification mixture.

Polythioethers that can be used include products obtained by condensing thiodiglycol alone or in combination with other glycols, alkylene oxides, dicarboxylic acids, formaldehyde, amino-alcohols, or aminocarboxylic acids.

Polycarbonate diols that may be used include glycols such as diethylene glycol, triethylene glycol, or those prepared by reacting hexanediol with formaldehyde. Suitable polyacetals can also be prepared by the polymerization of cyclic acetals.

Suitable polyolefin diols include hydroxy terminated butadiene homo- and co-polymers.

Suitable polysiloxane diols include polydimethylsiloxane diols.

Suitable bifunctional chain extenders include aliphatic diols such as ethylene glycol; 1,3-propanediol; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; 1,2-propanediol; 2-methylpropanediol; 1,3-butanediol; 2,3-butanediol; 1,3-pentanediol; 1,2-hexanediol; 3-methylpentane-1,5-diol; Diethylene glycol; Dipropylene glycol; And tripropylene glycol, and aminoalcohols such as ethanolamine, N-methyldiethanolamine and the like. Among these, 1,4-butanediol is preferable.

According to another embodiment, the TPU powder composition comprises a TPU based on an aromatic polyether. According to yet another embodiment, the TPU powder composition comprises an aliphatic, polyester based TPU. The latter TPU chemistry is particularly desirable due to its ability to more precise and accurate controlled melt flow properties (eg, melt flow index (MFI)) compared to the former.

Many suitable TPU compositions are commercially available. Depending on the application for which the powder composition is to be applied, often the MFI of the TPU composition is taken into account when selecting the TPU. In general, according to the exemplary uses described further below, it is desirable for the TPU to have an MFI of at least about 8 g / min when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg. In a further embodiment, the TPU preferably has an MFI of at least about 10 g / min when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg. In a still further embodiment, the TPU preferably has an MFI of at least about 12 g / min when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg.

BASF Corporation (Wynn Dodd, Mich.) And other commercial companies provide a variety of TPUs suitable for use in the present invention. One exemplary line of TPU grades is available from BASF Corporation under the trade name of ELASTOLLAN.

Although commercial sources of TPUs with MFIs within the preferred ranges are available, TPUs with lower MFIs may also be used as base TPUs. However, in order to sufficiently increase the MFI to the desired level, a small amount of water can be injected into the extruder containing the molten TPU. The addition of water in this manner causes the molten TPU polymer backbone to chain break, reducing molecular weight and increasing the MFI of the TPU. Chain cutting in this manner can be further accelerated by increasing the temperature and the axial speed of the extruder used. However, to prevent the MFI of the TPU from increasing in this manner to a level that negatively affects the resulting physical properties of the article formed from the TPU, other methods and materials are typically preferred.

In general, the prepared or supplied base TPU will be provided in a non-powder form (eg, as a pellet or granules). Thus, the base TPU and other optional components described below are transformed into powder after mixing and before use. The powder forming process is further described below.

Other ingredients

Other components may be included in the compositions of the present invention to improve or obtain the specific properties of the composition or components therein, such as the desired MFI of the base TPU. Depending on the method of making the base TPU or the commercial supplier of the base TPU, one or more additional components may already be present in the base TPU. However, if no other desired components are present, they may be added to the base TPU when preparing the compositions of the present invention.

These components include, for example, internal and other lubricants, glidants, heat stabilizers, light stabilizers, pigments (eg carbon black), antioxidants, plasticizers, fillers (eg talc and CaCO ₃ ) and Deglossants (eg, polyurea powder and various silicas). Those skilled in the art can select various components and various amounts of these components to achieve the desired properties without undue experimentation.

For example, a substance that reduces the porosity of the molten film of the composition during formation of an article from the composition, when the MFI of the composition of the present invention does not sufficiently minimize the capture of air between the molten film and the surface to be formed alone. This is advantageously added. If too much air is trapped, pores will appear on the outer surface of the formed article. In a variety of uses, particularly those involving parts for consumer use, no pores can be allowed at all before the article is rejected for aesthetic reasons. Although plasticizers can be added for this purpose, they move from the material surface (for example, it is often called "blooming", a phenomenon that causes fogging of the windshield when used in the instrument panel of vehicles). Because of their tendency to negatively affect the resulting physical properties of articles made from this material, the use of plasticizers in certain applications should be minimized.

According to one preferred embodiment of the invention, one or more lubricants are incorporated into the composition to reduce the pores in the resulting article without the disadvantages associated with achieving lower pores by increasing the MFI of the TPU alone. Another advantage of incorporating lubricant into the composition is that it can reduce or eliminate the need to use external mold release agents while forming molded articles from the composition.

In one embodiment, the compositions of the present invention comprise up to about 5% by weight of one or more internal lubricants based on the total weight of the composition. For example, from about 0.01 to about 1.0 weight percent of mono- and di-stearyl acid phosphates based on the total weight of the composition (eg, AX-71, Asahi Denka Kogyo Co., Ltd., Tokyo, Japan) Compositions, available under the trade names), have been found to be useful in accordance with the present invention. Although AX-71 is not commercially available as an internal lubricant, it has been found to be useful for this purpose. If the TPU contains aliphatic chemistry, then a smaller amount of lubricant is generally required to achieve the same results as when the lubricant is used with a TPU containing aromatic chemistry.

According to another embodiment of the present invention, one or more glidants are incorporated into the composition to reduce the pores in the resulting article without the disadvantages associated with achieving lower pores by increasing the MFI of the TPU alone. For example, a composition comprising precipitated amorphous silica (e.g., PS-200, available from the Venezuelan company Blassven C. A. under the PIROSIL tradename) is in accordance with the present invention. It can be used advantageously.

Compositions containing one or more such optional ingredients can eliminate the blooming phenomenon described above for the plasticizer. Thus, in a preferred embodiment, the plasticizer and other components that are likely to be transported are not present or contained in minimal amounts in the compositions of the present invention. Such other components include certain antioxidants, inhibited amine light stabilizers, UV stabilizers and other compounds known to promote undesirable blooming.

Formulation

The composition of the present invention comprises a powder composition blend comprising at least one base TPU and at least one other polymer. Such formulations are provided in powder form to facilitate their use in a variety of article forming processes that provide the substantial advantages discussed throughout this application. For example, one preferred use includes forming an article from a polymer using unique HVIF technology. Any of the ingredients described above may also be included in the powder composition formulations of the present invention to obtain the desired properties and to facilitate efficient processing of the desired composition. The ultimate blend can also be referred to as an "alloy" when a single phase is obtained.

In one embodiment, the powder composition blend of the present invention comprises at least about 10% by weight, based on the total weight of the composition, of at least one polymer other than TPU. For example, powder composition formulations comprising up to about 10 weight percent TPU and up to about 90 weight percent polyvinyl chloride (PVC) based on the total weight of the composition have been found useful in providing materials with improved properties. It became. The use of PVC in the powder composition formulations of the present invention provides a relatively cost effective material with improved advantages over PVC alone. When the powder composition formulation is prepared according to one embodiment of the invention, the base TPU component is present in an amount of about 5 to about 50 weight percent based on the total weight of the composition. In a more preferred embodiment, the base TPU component described above is present in an amount of about 10 to about 30 weight percent or about 15 to about 25 weight percent based on the total weight of the composition. Remaining ingredients include PVC and other optional ingredients.

One specific component preferred for incorporation in certain embodiments of the powder composition formulations of the present invention is Alcrine from Advanced Polymer Alloys division of Ferro Corp., Wilmington, Delaware. (ALCRYN) is a melt processible rubber available under the trade name. Such melt processible rubber may be present in the composition in an amount of about 5 to about 50 weight percent based on the total weight of the composition. In further embodiments, such meltable rubber may be present in the composition in an amount of about 10 to about 40 weight percent based on the total weight of the composition. In still further embodiments, such melt processable rubber may be present in the composition in an amount of about 15 to about 30 weight percent based on the total weight of the composition.

Combining the TPU and PVC in a unique powder composition formulation results in a material having an improved failure mode compared to such materials that essentially comprise PVC. PVC typically exhibits a brittle fracture mode, but the combination of PVC and TPU has been found to exhibit a more ductile failure mode. Preference is given to using materials having a ductile failure mode in various applications. The use of air ductile materials with increased ductility in passenger compartments is one example of such use. If a material exhibiting brittle fracture is used to make the airbag, the airbag tends to shatter when used at lower temperatures (eg, especially at temperatures below about −40 ° C.). Thus, in order to effectively use airbags in cooler climates, improved materials have been desired.

The powder composition formulations of the present invention provide such an improved material. The compositions of the present invention can successfully pass the rigorous tests imposed on manufacturers of vehicles for airbag materials.

Formation of powder

The powder composition of the present invention is prepared such that the composition has an average particle size and particle size distribution depending on the intended use and the processing method of the article made from the composition. Powder compositions of various particle sizes can be prepared. In one exemplary embodiment, the powder composition of the present invention has an average particle size of about 80 μm to about 300 μm. In a further embodiment, the average particle size is at least about 100 μm, or in still further embodiments even at least about 200 μm.

Particle size analysis can be performed using any suitable apparatus and method, depending on the level of knowledge of those skilled in the art. In certain applications, the particle size distribution is preferably a single peak, such as the distribution shown in FIG. 1. According to the particle size distribution shown in FIG. 1, 50% of the screened particles had a size of about 128 μm or less, and 95% of the screened particles had a size of about 253 μm or less. In other applications, the particle size distribution is preferably bimodal, such as the distribution shown in FIG. 2. According to the particle size distribution shown in FIG. 2, 50% of the screened particles had a size of about 230 μm or less, and 95% of the screened particles had a size of about 423 μm or less. The particle size distributions shown in FIGS. 1 and 2 were obtained using well-known methods and particle analysis equipment available from Microtrac, Inc. (Mongomeryville, Alabama).

The components of the composition are first mixed in an amount selected in proportion to the desired overall formulation and intended use. This occurs during mixing of the base TPU, where water can optionally be injected into the mixture in small amounts sufficient to increase the MFI of the TPU as needed (e.g., trace amounts of water will be sufficient for this purpose).

While not necessarily premixing all of the components of the composition prior to transformation into a powder, it is desirable to mix components that require such transformation before formation into a powder. Alternatively, although not desired because of efficiency, the composition may be formed by a number of mixing and powder forming steps.

Mixing may occur in the presence of heat and / or pressure to obtain a mixture in which the base TPU and any of the components are substantially uniformly mixed. For example, the components are mixed in the extruder and exit from the extruder via a pelletizer. Once processed in this manner, the resulting pellets can be transformed into powders of the desired particle size and distribution.

In order to transform the mixed composition into a powder of the desired particle size and distribution, any suitable powder forming technique can be used. For example, the powder can be prepared from the mixed composition using mechanical techniques such as cryogenic polishing or hammer milling.

Note that a single pass through the cryogenic polishing process is generally not sufficient to produce a powdered composition having the desired particle size distribution for subsequent use, including the HVIF technique described further below. Other powder forming techniques may be used and may be more efficient, but screening and recycling steps following cryogenic polishing may be used to achieve the desired particle size distribution. See US Pat. No. 5,597,586, which discloses a method of modifying the composition into useful powder-like forms using underwater micropelletizing. In addition, US Pat. No. 5,654,102 discloses a method of modifying a composition with micropores of a size suitable for a particular use, such as slush molding.

3 illustrates an exemplary embodiment of a method of making a powder composition of the present invention. Details and modifications to the steps and equipment described herein are within the knowledge of those skilled in the art.

As shown in FIG. 3, the first high-strength mixer 10 operating at a temperature of about 120 ° C. to about 140 ° C. (eg, of the Henschel type such as available from Mitsui Mike, a Japanese company) A Henschel-type variable speed mixer is provided for the initial mixing stage. The high intensity mixer 10 is loaded with a mixture 12 of the base TPU and other components (eg, lubricants, glidants, stabilizers, pigments, etc.) required for the particular application desired. Optionally, additional other components 14 needed for the particular application are added to the high intensity mixer 10 after being preheated (eg, in certain embodiments, preheated to a temperature of about 80 ° C. to about 90 ° C. Plasticizer may be added later).

The mixture is then transferred from the high intensity mixer 10 to a low intensity mixer 16 which simultaneously cools the mixture (eg, a Henschel type chiller mixer operating at a speed of about 110 rpm). Once the powder composition blend is formed, another polymer 18 (eg, vinyl chloride) can be added to the mixture and processed in the low intensity mixer 16. Once the mixture reaches a temperature of about 50 ° C., it can be discharged to the hopper 20 for further processing to complete the dry blending operation 22.

From the hopper 20, the mixture passes through a screener 24 (eg, a vibrating screener with a 10 mesh screen, such as a Sweco-type screener). Any oversize component 26 is discarded and the remaining components are then subjected to an extrusion operation 32 which is left after being transferred to the vessel 28 where the residual components are melt blended (eg For example, a twin screw such as an extruder 30 (eg, a Leistritz 27-mm co-rotating extruder of the name MIC 27 GL / 40D) for a temperature of about 180 ° C. and a speed of about 350 rpm. Remain in dry powder form until transferred to the extruder). Optionally, water can be injected into the extruder to assist in adjusting the MFI of the material as desired. After the material is discharged from the extruder 30, it passes through a water cooler 34 and then pelletizer 36 (e.g., Conair Group, Inc., Pittsburgh, Pennsylvania). Strand pelletizer with drip tray, such as available from. The material exits the pelletizer 36 in the form of pellets 38.

Thereafter, the cryogenic polishing operation 40 is performed on the pellet 38. First, pellet 38 is cooled in liquid nitrogen 42 and then obtained from wear mill 44 (e.g., Midwest Elastomers, Inc., Waffaconetta, Ohio). Cold cryogenic wear mill). From this wear mill 44, pellets pass through the first cyclone separator 46 to the screener 48, whereby particles of the desired dimensions can be moved to the second cyclone separator 5. Oversize particles 52 are returned to liquid nitrogen 42 for further milling. On the way to the second cyclone separator 50, the screened composition can be heated using, for example, dry forced air. Eventually, the resulting powder composition 54 exits the second cyclone separator 50, where the powder composition is packaged or used for the formation of an article made from the powder composition 54. Stored.

Usage

The TPU compositions of the present invention can be used to form various articles. Advantageously, the compositions of the present invention can provide improved surface finish on various articles made from these compositions. For example, due to the relatively uniform and small particle size of certain embodiments of the powder compositions of the present invention, polymer skins formed from these powder compositions often have little surface defects compared to polymer skins made from other compositions.

As such, a first exemplary use of the compositions of the present invention relates to high speed impact melting (HVIF). This technique promotes polymer skin formation using the formulation of the present invention. In this embodiment using HVIF technology, the TPU powder composition preferably has an average particle size corresponding to the particle size distribution of FIG. 1. Smaller size particles typically form a waste because these small particles often cannot reach the target substrate during the HVIF process, which is often designed to use large size particles, and therefore it is desirable to exclude them. . The particle size distribution for the composition used in the HVIF process is preferably relatively unimodal.

According to the HVIF technology, the composition is heated and then sprayed onto the mold surface to form the article. In one embodiment, the composition is heated to the melting point using a hot nitrogen or oxygen environment. Once fluidized in this manner, the composition is directed to a substrate (eg nickel plated steel) maintained at approximately room temperature. Once the composition is placed on the substrate, the composition cools to form an article. In one exemplary embodiment, the article is a continuous solid membrane (eg, a polymer skin). In certain embodiments using HVIF technology, the mold surface is textured to provide the article with the desired surface finish. For example, the mold surface may be formed to represent leather when making articles such as instrument panels, armrests, headrests, door panels and other items in the passenger compartment of the vehicle.

One exemplary commercial source of equipment useful for this HVIF technology is the Wideman Company, Inc., Ft. Myers, Florida. Further details on one embodiment of this technology are described, for example, in US Pat. No. 5,285,967, assigned to Wideman Company, Inc. and discussing high speed oxygen fuel (HVOF) spraying technology and related equipment. It is. The HVOFs described herein utilize a continuous combustion process that produces exhaust gas velocities of about 1,200 to 1,500 meters / second (4,000 to 5,000 feet / second) or less. To produce a gas having this discharge rate, fuel gases such as propylene or hydrazine and oxygen are combusted in an internal combustion chamber under high pressures of about 0.4 to 0.6 MPa (60 to 90 psi). The hot exhaust gas exits the combustion chamber through the exhaust port, expands into an extended nozzle that meets the powdered composition, and is fed into the nozzle with an inert carrier gas such as nitrogen to be confined by the exhaust gas stream. The powdered composition melts here and exits the nozzle with a high velocity jet stream having a length of about 9 decimeters (36 inches) and a stream diameter of about 1.2 centimeters (1/2 inch). Using this technique, a sufficiently dense coating of a composition with properties superior to those obtained using other techniques can be produced.

Other uses of the compositions of the present invention for the formation of articles relate to conventional powder coating techniques, including fluidized bed, electrostatic spray, and thermal spray techniques. Other applications mentioned above include conventional molding techniques such as slush molding and rotational molding.

According to the fluidized bed technique, the heated metal part is immersed in an aerated bed of the powdered composition. The powder melts on the heated part to form a smooth continuous film that encapsulates the metal. This method may also be carried out in what is referred to as the "fluid bed". The fluidized bed has three main zones: (1) a tower powder hopper in which the powder is maintained; (2) a porous plate capable of passing air therethrough; And (3) a sealed bottom air chamber. When pressurized air is blown into the air chamber, this air passes through the plate, causing the powder to float or fluidize. This fluidization allows the metal parts to be coated and travel through the powder with little resistance during the dipping process. Alternatively, the cold substrate may be placed on a layer of fluidized particles that are charged by friction and cling to the substrate. The coated substrate may then pass through a heating zone or nip to melt the coating.

According to the electrostatic spraying technique, the powdered composition is dispersed in the air stream and passes through the corona discharge zone. In this corona discharge zone, the powder gains an electrostatic charge. The charged powder is attracted and then deposited on the grounded substrate. Usually at room temperature the electrostatically coated substrate is then placed in an oven where the powder melts and a coating is formed.

Known thermal spray processes are characterized by their heating method. Heating methods using chemical combustion heating include powder flame spraying. Heating methods using electrical heating include plasma flame spraying. Among these methods, plasma flame spray is predominantly used.

Plasma flame spraying is primarily a method in which deposition of molten material is enabled by using a highly directional gas stream. An ionized gas consisting of plasma, free electrons, cations, atoms, and molecules is used as a means of heating the powdered composition to a molten state at high temperature (eg, approximately 15,000 ° C.) by using an electric arc. . To generate an arc, a selected gas, such as argon or nitrogen, flows between the anode and the cathode. An arc is generated in the gas flow between the anode and the cathode, which heats the composition and accelerates it to the substrate. After impinging on the substrate, the composition is heated to melt to form a coating.

In contrast to plasma flame spraying techniques, conventional slow air open powdered flame spraying utilizes combustion as a means of heating the powder. The powdered composition, combustion air and fuel move to an open mixed combustion chamber where it is ignited. Ignition of the fuel and gas mixture melts the composition, which is then carried by air from the combustion chamber to provide a coated substrate. Because of the lower speed of the composition that impinges on the substrate in this way compared to the HVIF technique described above, the resulting coatings often have insufficient bond strengths and do not, by themselves, provide a repeatable high production rate process.

Slush molding uses an open end mold design to form an article (eg, a dashboard of a vehicle). In this embodiment, the TPU powder composition preferably has an average particle size larger than the average particle size desired for use with the HVIF technology. For example, a composition having an average particle size corresponding to the particle size distribution shown in FIG. 2 can be used. In this embodiment, the particle size distribution of the compositions used in this process need not be relatively unimodal as in the case of using such compositions used in the HVIF process described above. Rather, particle size distributions of bimodal, such as those obtained from cryogenic polishing of TPU, can be used.

Rotational molding is another technique for forming articles (eg, armrests and headrests in passenger compartments of vehicles, and other articles such as recreational balls). Compared to slush molding, the rotational molding process is operated on one axis of rotation using a closed mold design. In addition, although bimodal particle size distribution can also be used in the case of rotational molding, the distribution is typically of a larger average particle size than the average particle size used for slush molding.

According to another suitable method of forming an article using one of the above or a powdered formulation, the article is formed from the TPU and TPU powder composition combinations of the invention. By fusing the improved powder compositions of the present invention using processing techniques such as HVIF technology, excellent articles can be made. Such articles are useful to meet industrial needs, including the manufacture of polymeric articles used in passenger compartments of vehicles.

1 shows a unimodal particle size distribution associated with a powder composition useful for forming an article according to the high speed impact melting technique in accordance with the present invention.

2 shows a bimodal particle size distribution associated with a powder composition useful for forming an article according to the slush molding technique according to the present invention.

3 is a schematic flowchart of an exemplary method for forming a powder composition of the present invention.

Further examples and applications of the present invention are described in the following non-limiting examples.

Example  One

Base TPU was obtained under the trade name Elastolan LJ 56/187 from a commercial supplier (Basp Corporation, Wynndot, Mich.). When tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg, the MFI of the base TPU was measured at 55 g / 10 min. When tested according to ASTM D1238 at a lower temperature of 170 ° C. and the same weight of 2.16 kg, the MFI of the base TPU was measured at 27 g / 10 min.

In high-strength mixers, the base TPU was subjected to internal lubricants [AX-71, mono- and di-stearyl acid phosphates available from Amfine Chemical, Mie, Japan] and pigments [Cabot, Boston, Mass.] Corp.) under carbon black available under the REGAL BLACK tradename. The high intensity mixer was operated at a temperature of about 120 ° C to about 140 ° C. The mixture was then transferred from a high intensity mixer to a low intensity mixer operating at a speed of about 110 rpm and mixed and the mixture cooled simultaneously. When the mixture reached a temperature of about 50 ° C., the mixture was discharged into a hopper and then passed through a screener. The screened particles were then fed to a twin screw compressor operating at a temperature of about 180 ° C. and a speed of about 350 rpm. After exiting the extruder, the mixture was passed through a water cooler and then sent to a pelletizer to form pellets. The pellet was then subjected to cryogenic polishing operations.

Once the powder had been formed, the glidant (PS-200, available under the Filosil brand from Venezuela company Glaben C. A.) was mixed with the powder in an amount of 0.15% based on the total weight of the composition. In the composition thus formed, the amount of base TPU was 99.05%, the amount of internal lubricant was 0.30%, the amount of pigment was 0.50%, and all of the above weight percentages were based on the total weight of the composition.

Example  2

In high-strength mixers, the base TPU (Elastolan LJ 56/187, available from BASF Corporation, Wynn Dot, Mich.) Is an internal lubricant (AX-71, mono- and di-steas available from Ampine Chemical, Mie, Japan). Aryl acid phosphate) and pigments (carbon black dispersion, available under the trade name STAN-TONE HCC-20327 BLACK from Polyone Corp., Aven Lake, Ohio). This mixture was processed as described by reference in Example 1 to form a powder composition. In the powder composition thus formed, the amount of base TPU was 98.2%, the amount of internal lubricant was 0.2%, the amount of pigment was 1.6%, and all weight percentages were based on the total weight of the composition.

Example  3

The method described by reference in Example 1 and FIG. 3 was used to form the powder composition blend. This powder composition blend is available from 30.0% base TPU (Elastolan LJ 56/187, BASF Corporation, Wynndot, Michigan), 0.1% internal lubricant (AX-71, available from Ampine Chemical, Mie, Japan). Mono- and di-stearyl acid phosphate), 33.3% polyvinyl chloride resin suspension [SUSP RESIN 200F (DPK), available from Oxyvinyl Corp., Dear Park, Texas], 1.4 % Mixed stabilizer (CPS 507, available from Ampine Chemicals, Hopkinsville, KY), 0.1% fatty acid ester (LS-10, available from Ampine Chemical, Mie, Japan), 0.9% phosphite stabilizer (CPL-1551 D, available from Ampine Chemical, Hopkinsville, KY), 2.8% Pigment Dispersion (VM6432 9779 MD GRAY MB, Poly, Aven Lake, Ohio) Available from Corporation), 28.1% n-octyl trimellitate plasticizer (SYNPLAST NOTM ELECTRICAL, available from Synergistics, St. Remy, Canada), and 3.3% polyvinyl chloride Resin dispersion (VINNOLIT P70, available from Vinnolit, Ismaning, Germany). All of the above weight percentages are based on the total weight of the composition.

Example  4

The method described by reference in Example 1 and FIG. 3 was used to form the powder composition blend. This powder composition blend is available from 30.0% base TPU (Elastolan LJ 56/187, BASF Corporation, Wynndot, Michigan), 0.1% internal lubricant (AX-71, available from Ampine Chemical, Mie, Japan). Mono- and di-stearyl acid phosphates), 32.5% polyvinyl chloride resin suspension (suspension 200F (LVL), available from Oxyvinyl Corporation, Dear Park, Texas), 0.1% mixed stabilizer (CPS 507, Available from Ampine Chemicals, Hopkins, Kentucky), 0.1% fatty acid ester (LS-10, available from Ampine Chemicals, Mie, Japan), 0.7% phosphite stabilizer (CPL-1551 D, Kentucky Hopkinsville) Available from Ampine Chemical, Inc., 1.6% Pigment Dispersion (0928189 642H V DK PEWTER MB, Poly One Corporation, Aven Lake, Ohio). Available from), 30.2% n-octyl trimellitate plasticizer (Shinplast Normlectic, available from Synergistics, St. Remy, Canada), and 3.9% polyvinyl chloride resin dispersion (vinolith P70, Germany) Available from Vinolit, Ismaning). All of the above weight percentages are based on the total weight of the composition.

Various modifications and variations of the present invention will be apparent to those skilled in the art without departing from the spirit and scope of the invention, the scope of the invention being defined by the appended claims. The steps recited in any of the method claims below do not necessarily have to be practiced so that they are cited. Those skilled in the art will be aware of changes in carrying out the steps from the order in which they are cited.

Claims (38)

A thermoplastic powder composition suitable for forming into an article using high speed impact melting, One or more thermoplastic polyurethanes having a melt flow index of at least about 8 g / 10 minutes when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg; One or more internal lubricants present in an amount of about 5% by weight or less based on the total weight of the composition; And Optionally one or more glidants, A thermoplastic powder composition having a uni-modal particle size distribution. The thermoplastic powder composition of claim 1, wherein the thermoplastic polyurethane comprises an aliphatic thermoplastic polyurethane. The thermoplastic powder composition of claim 1, wherein the thermoplastic polyurethane comprises an aromatic thermoplastic polyurethane. The thermoplastic powder composition of claim 1, wherein the thermoplastic polyurethane comprises a polyether based thermoplastic polyurethane. The thermoplastic powder composition of claim 1, wherein the thermoplastic polyurethane comprises a polyester-based thermoplastic polyurethane. The thermoplastic powder composition of claim 1, wherein the thermoplastic polyurethane comprises a thermoplastic polyurethane based on an aromatic polyether. The thermoplastic powder composition of claim 1, wherein the thermoplastic polyurethane comprises a thermoplastic polyurethane based on an aliphatic polyester. The thermoplastic powder composition of claim 1, wherein the composition comprises from about 0.01 to about 1.0 weight percent mono- and di-stearyl acid phosphate, based on the total weight of the composition. The thermoplastic powder composition of claim 1, wherein the composition is essentially free of ingredients that are prone to blooming migration in articles made from the composition. The thermoplastic powder composition of claim 1, further comprising at least one component selected from heat stabilizers, light stabilizers, pigments, antioxidants, plasticizers, fillers and matting agents. An article made from the thermoplastic powder composition of claim 1. The article of claim 11, wherein the article comprises a polymeric skin subcomponent in a further article for the passenger compartment of the vehicle. The article of claim 12, wherein the additional article is selected from instrument clusters, door panels, armrests, headrests, center consoles, and airbags for passenger compartments of vehicles. A powder composition formulation comprising at least one thermoplastic polyurethane and at least one other polymer. The powder composition formulation of claim 14, wherein the other polymer is included in an amount greater than about 10% by weight of the total composition. The powder composition formulation as claimed in claim 14, wherein the other polymer comprises polyvinyl chloride. The powder composition formulation as claimed in claim 14, wherein the other polymer comprises polyvinyl chloride in an amount up to about 90% by weight of the total composition. The powder composition formulation as claimed in claim 14, further comprising a melt processable rubber. The powder composition blend of claim 14, wherein the composition comprises one or more thermoplastic polyurethanes in an amount of about 5 to about 50 weight percent of the total composition. The powder composition formulation of claim 14, wherein the composition comprises one or more thermoplastic polyurethanes in an amount of about 10 to about 30 weight percent of the total composition. The powder composition blend of claim 14, wherein the composition comprises one or more thermoplastic polyurethanes in an amount of about 15 to about 25 weight percent of the total composition. 15. The powder composition formulation as claimed in claim 14, having a unimodal particle size distribution. 15. The powder composition blend of claim 14, having a bi-modal particle size distribution. An article made from the powder composition combination of claim 14. The article of claim 24, wherein the article comprises subcomponents of the polymer skin in a further article for the passenger compartment of the vehicle. 27. The article of claim 25, wherein the additional article is selected from instrument clusters, door panels, armrests, headrests, center cones, and air compartments for passenger compartments of vehicles. The article of claim 25, wherein the additional article comprises an airbag for a passenger compartment of the vehicle. A method for producing the thermoplastic powder composition of claim 1, Providing a thermoplastic polyurethane; Mixing the thermoplastic polyurethane with one or more optional components; And Transforming the thermoplastic polyurethane and optional components into a powder having a unimodal particle size distribution. 29. The method of claim 28, wherein the thermoplastic polyurethane and optional components are transformed into powder using cryogenic polishing, screening, and recycling steps. The water of claim 28 wherein the thermoplastic polyurethane melts to increase the melt flow index of the thermoplastic polyurethane to greater than about 8 g / 10 minutes when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg. Further comprising reducing the molecular weight of the thermoplastic polyurethane by injecting the same into an extruder. A method of making an article from the thermoplastic powder composition of claim 1, comprising: Providing a thermoplastic powder composition; And Forming an article from the thermoplastic powder composition using a high speed impact melting technique. The method of claim 31, wherein no external mold release agent is used to form the article. A process for preparing the powder composition blend of claim 14, wherein Providing a thermoplastic polyurethane; Mixing the thermoplastic polyurethane with other polymers and optional ingredients to form a blend; And Transforming the mixture into a powder having a predetermined particle size distribution. A method of making an article from the powder composition blend of claim 14, the method comprising: Providing a powder composition blend; And Forming an article from the thermoplastic powder composition blend. 35. The method of claim 34, wherein the article is formed using high speed impact melting, fluidized bed powder coating, electrostatic spraying, thermal spraying, slush molding, or rotational molding techniques. A thermoplastic powder composition suitable for forming into an article using slush molding, At least one thermoplastic polyurethane having a melt flow index of at least about 8 g / 10 min when tested according to ASTM D1238 at 190 ° C. and a weight of 2.16 kg; One or more internal lubricants present in an amount of about 5% by weight or less based on the total weight of the composition; And Optionally one or more glidants, Thermoplastic powder composition having a bimodal particle size distribution. An article made from the thermoplastic powder composition of claim 36. 37. A method of making an article from the powder composition of claim 36, wherein Providing a powder composition; And Forming an article from the thermoplastic powder composition.

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