JPS6222771B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to rubbery compositions and molded articles made from them. The present invention relates in one aspect to a method of forming a product. Another aspect of the invention relates to molding compositions. Yet another aspect of the invention relates to the use of microwave frequency energy in the molding of thermoplastic compositions. Naturally grown crepe rubber has been successfully used in the manufacture of shoe soles for half a century. This rubber is made from high-quality natural rubber. After adding preservatives to natural rubber latex, it is coagulated. This material is dried and formed into thin gauge sheets in a special mill or calender. This sheet is then drummed into a drum. Roll and manufacture. Once the desired thickness (3/16 to about 1/2 inch) is achieved, the material is cut from the drum into sheets. This sheet is wrapped to protect it from light and contamination and is commonly sold for use in the manufacture of shoe soles. The amount of material rejected during the cutting of soles and wedges can be close to 25% or even more of the sheet material. Some of the disadvantages of naturally grown crepe rubber are listed below. (1) Raw material costs are high. (2) High rate of rejected materials that cannot be directly reused. (3) There is variation in color tone within the range of two standard colors. (4) The surface is sticky. (5) Because static electricity attracts dirt to sticky surfaces, items that cannot be washed become useless after a very short period of use. (6) Poor resistance to sutures. The inventors have found that all of the above-mentioned drawbacks can be overcome by producing an imitation crepe rubber as described below. Furthermore, imitation crepe rubber has better abrasion resistance than natural crepe rubber, so it has the advantage that the sole lasts longer. The use of a simulated crepe rubber with an expanded interior due to the microporous structure provides a more economically superior molding composition without reducing abrasion resistance. The present invention provides a molded product imitating the appearance of naturally grown crepe rubber. The composition of the molded article includes (1) a styrene/butadiene linear or radical block copolymer (the content of polymerized styrene is about 20 to about 50% by weight, preferably about 25 to about 35% by weight of the total block copolymer); %, the remainder being polymerized butadiene), and (2) resinous solid polymers of vinyl-substituted aromatic compounds (block copolymers 100
(within the range of about 10 to about 60 parts). In carrying out the present invention, a method for manufacturing a molded article imitating the appearance of naturally grown crepe rubber is provided, which is as follows. A resinous polymer of a styrene/butadiene linear or radical block copolymer (the content of polymerized styrene is within the range of about 25 to about 35% by weight of the total block copolymer) and a vinyl-substituted aromatic compound. (within the range of about 10 to about 60 parts per 100 parts of block copolymer) is combined with a polarizing agent in an amount sufficient to cause rapid heating using microwave frequency energy. This composition is placed in a mold having a molding surface shaped like a mold for naturally grown crepe rubber (or has one molding surface shaped like a mold for naturally grown crepe rubber), and is heated using microwave energy. The composition is melted and molded and removed from the mold as a product having the appearance of naturally grown crepe rubber. In another embodiment of the invention, by dispersing a sufficient amount of blowing agent throughout the molding composition,
The foaming agent is activated by the effect of temperature rise during the molding process and generates gas, which creates a normal dense polymer skin (formed in contact with the molding surface that gives the appearance and warp of naturally grown crepe rubber). The molded skin has a microporous structure (with the appearance of naturally grown crepe rubber). Comparing a microporous structure protected by a thick skin with one made without a blowing agent, the former has intact abrasion resistance, improved opacity and a softer feel. The microporous structure is less dense than those made without blowing agents, resulting in an overall savings in molding composition. In the practice of this invention, linear and radical teleblock copolymers, which are normally solid, are used, with the content of polymerized styrene being about 25 to about 35% of the total block copolymer.
% by weight, with the remainder being polymerized butadiene, and is characterized by a high degree of tensile strength and elongation in its native (i.e., unvulcanized) state], but generally has a uniform concentration. It is most useful in giving motsu-type products the appearance of naturally grown crepe rubber. Mold products containing elastomers with the above styrene content most closely resemble natural crepe rubber in appearance, feel, elasticity and abrasion resistance. The presently preferred polymers are linear or radical 30/70 styrene polymers having an inherent viscosity in the range of about 0.8 to 1.6 as determined by the method described in U.S. Pat. No. 3,278,508, column 20, note (a). It is a butadiene block copolymer. The content of polymerized styrene in the linear or radical styrene/butadiene block copolymer used to form the microporous structure preferably ranges from about 25 to about 35% by weight. Also, as mentioned above, the preferred polymer for forming the microporous structure is about 0.8
A linear or radical 30/70 styrene/butadiene copolymer having an inherent viscosity in the range of 1.6 to 1.6. Other polymers used to form this composition include resinous solid polymers of vinyl-substituted aromatic compounds (e.g. styrene, alpha-methylstyrene, etc.) [which may be used alone or with acrylonitrile]. or a conjugated diene (e.g. butadiene)
may be copolymerized with monomers such as Such homopolymers or copolymers generally have a molecular weight of about 1.04
(ASTM D-792) and a tensile strength of about 5000 to about 12000 psi (34.5-82.7 MPa) (ASTM D-638) and about 23 Shore A hardness at °C is within the range of about 35 to about 95 (ASTM D-2240). This polymer is mixed with an elastomer in the range of about 10 to about 60 parts of resinous polymer per 100 parts of block copolymer. Resinous polymers can be used individually or poly(α-
The presently preferred composition contains a mixture of methylstyrene (within the range of about 20 to 35 parts per 100 parts of block copolymer) and crystalline polystyrene (within the range of about 10 to about 25 parts per 100 parts of block copolymer). It can also be used as a mixture with. A polarizing agent is incorporated into the composition of the present invention to ensure melting of the composition in a microwave field. The polar compounds used in the present invention are usually liquid or solid in nature and include simple or polymeric alkylene glycols and their mono- and dialkyl ethers, ethanolamine and isopropanolamine and their hydrocarbyl-substituted derivatives, and mixtures thereof. selected. Typical examples are shown below. ethylene glycol,
1,2-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol,
1,6-hexylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, thiodiethylene glycol, etc.; approx.
Polyethylene glycol having an average molecular weight within the range of from 200 to about 6000; polypropylene glycol having an average molecular weight within the range of from about 400 to about 2000; having an average molecular weight within the range of up to about 6000 and from about 30 to about 90% by weight Poly(ethylene)-poly(propylene) containing % ethylene oxide
Glycol mixtures; monomethyl, monoethyl and monobutyl ethers of ethylene glycol, propylene glycol and diethylene glycol; monomethyl and monoethyl ethers of triethylene glycol; dimethyl and diethyl ethers of diethylene glycol, dipropylene glycol and trimethylene glycol; based on ethanol and isopropanol Alkanolamines [e.g. mono-, di- and triethanolamine, mono-, di- and triisopropanolamine, methylethanolamine, dibutylethanolamine, phenyldiethanolamine, di(2
-ethylhexyl)ethanolamine, dimethylisopropanolamine, dibutylisopropanolamine, etc.]; and mixtures thereof. Other polar compounds are also effective, such as liquid acrylonitrile/butadiene polymers, blends of acrylonitrile butadiene and homopolymers of polyvinyl chloride, and styrene/acrylonitrile copolymers. Further examples of polarizing agents that meet this purpose include the following. Glyceryl diacetate (diacetin), di(2-hydroxyethyl)-5,5-
Dimethylhydantoin (Dantocol DHE, Glycol
Chemical, Inc., Greenwich, conn.), styrene acrylonitrile resin (SAN
124 (available from Dow Chemical) and resinous ethylene-vinyl acetate copolymers which are normally solid. Particularly suitable polarizing agents include triethanolamine and diethylene glycol or polyethylene glycol (eg Carbowax 1540) in a total amount of about 5-8 parts php. Other additives that can be used include fillers, plasticizers, processing aids, resins, stabilizers, and the like. The final composition can be shaped into a dense product (ie, a product with a specific gravity of about 1). Polarizing agents selected from solid nitrile rubber, polychloroprene polymers and carbon black are not suitable for use in the practice of this invention. This is because compositions containing such polarizing agents do not tend to flow easily under the low molding pressures used in the method of the present invention. Sufficient polarizing agent is included in the compositions of the present invention so that when the composition is placed in a microwave field, it will rapidly heat and soften. Generally, the amount of polarizing agent used is within the range of about 0.5 to about 20 parts by weight per 100 parts of thermoplastic elastomer, and from about 0.75 to about 10 parts by weight, taking into account the economics associated with suitable microwave reaction. is more preferable. The heating time is selected to allow rapid softening of the composition to moldable softness without adverse effects from localized overheating. Typically used heating times can vary from about 4 seconds to about 4 minutes. However, from a commercial standpoint, heating times in the range of about 4 to 55 seconds are used to achieve favorable production rates, and this is the preferred range. The average heating temperature to soften the composition is approximately 250-320〓 (120-160
℃) or higher temperatures can be used. Other ingredients that can be used to make the compositions of the invention include perfumes, pigments, and fillers (eg, silica, clay silicates, Wollastonite, calcium carbonate, glass beads, glass fibers, etc.). If desired, plasticizers that are compatible with thermoplastic elastomers and other resinous polymers can also be used. Examples of such plasticizers include naphthenic petroleum (eg, ASTM Type 104), esters of adipic acid and phthalic acid, and the like. Processing aids include metal stearates (eg, calcium stearate, zinc stearate), silicones, natural and synthetic waxes, and the like. If desired, antioxidants and UV stabilizers selected from suitable commercial products can also be added. Examples of antioxidants include thiodipropionate esters (e.g. dilauryl thiodipropionate), hindered phenolic antioxidants [e.g. 2,6-di-t-butyl-4-methylphenol, octadecyl] 3-(3,5-di-t-butyl-4-hydroxyphenyl)]propionate, thiodiethylenebis(3,5-di-t-butyl-4-hydroxy)hydrocinamate], etc. UV stabilizers include 2(2'-hydroxy-5'-methylphenyl)benzotriazole, 2
-Hydroxy-4-n-octoxybenzophenone, [2,2'-thiobis(4-t-octyl-phenolate)]-n-butylamine-nickel (), and the like. When using such components, thermoplastic elastomers (php) are generally used.
The following amounts per 100 parts by weight: filler 10 to 150 php, plasticizer 20 to 50 php; antioxidant
0.1 to 1php, UV stabilizer 0.1 to 3php. In another embodiment, a product is manufactured using a composition that is generally the same as for manufacturing a dense product except for the use of a chemical blowing agent. Such products have a normal dense epidermis and a microporous interior. The amount of blowing agent used can vary over a very wide range (eg, from about 0.5 to 10 php of the total polymer mixture) depending on the specific gravity of the desired final product. For example, to produce a microporous product with a specific gravity of about 0.8-0.9, which is currently the most preferred range, a total of about 3-6 php of blowing agent may be used. Mold products with specific gravity less than about 0.7 begin to lack tear strength and are therefore not desirable for the use proposed in this invention. A suitable chemical blowing agent (generally a nitrogen liberator)
The decomposition temperature in the composition is about 140°-200°C. Typical commercially available compounds include N,
N′-dinitrosopentamethylenetetraamine,
Includes 4,4'-oxybis-(benzenesulfonylhydrazide) (OBSH) and azobisformamide (azodicarbonamide) (ABFA).
A mixture of about 50/50 by weight of OBSH and ABFA is generally suitable. OBSH is useful because it can act as a blowing agent as well as a crosslinking agent. ABFA is useful because it is a flame retardant because it does not burn, and because it is easily dispersed in compositions and becomes a good source of nitrogen gas when decomposed. The decomposition temperature can be adjusted to some extent by changing the ratio of OBSH to ABFA, for example. The formulation can be mixed prior to the molding operation by methods known in the art. If all ingredients are in liquid and/or granular form, a high-power mixer (eg Henschel mixer) can be used. The ingredients can be mixed at a temperature above the melting point of the polymer used, provided that if a blowing agent is used, the temperature must be below the decomposition temperature of any blowing agent. Melt blending can be performed using a roll mill, Banbury mixer extractor, etc. However, it is preferred to convert the resulting molten product into compound slabs or free-flowing granules of suitable dimension by conventional methods (eg, pelletizing, milling, etc.). The molds used to mold the compositions of the present invention are generally made of inexpensive and relatively low strength materials, including silicone rubber, polysulfide rubbers, polyurethane, plaster, cast aluminum, and the like. The nature of the mold depends on the molding method used. If the composition of the invention is placed in a mold and the set is preheated by microwave energy, the mold used should be made of a material (e.g. silicone rubber) that has a lower dielectric loss factor than the composition of the invention. is preferred. It is within the scope of the present invention to preheat the composition in a container with a low dielectric loss factor (eg, glass ceramic) and then transfer it to a mold for the actual molding step, made of metal or the like. Generally, the composition is placed in a silicone rubber mold, the top of the mold is covered with a silicone rubber sheet or silicone release paper (e.g., paper coated with a release agent such as silicone), and the set is Place it between high frequency electric field plates that are part of a commercial molding machine. The top plate is lowered into contact with the release paper covering the mold, and the mold and composition are subjected to microwave energy to preheat for the desired period of time. After preheating to the softening temperature, the composition is subjected to a pressure sufficient to compression mold it (e.g., about 10 to about 200 psig (68.9-1380 kpa)) for a period generally within the range of about 0.1 to about 10 times the preheat period. Add. After the pressure is removed, the set is preferably placed in a separation zone to cool the mold and contents, after which the mold product is removed. Using a rotary table or the like equipped with multiple molds, molded parts can be produced at commercially viable rates. Separating the heating and cooling zones increases production rates and saves power and water consumption. An essential condition of the mold used for molding the product according to the invention is that the surface of the mold product that contacts the creped surface is made to be similar to naturally grown crepe rubber. Of course, the best way to do this is to make the surface of the mold a mold of the surface of cultivated crepe rubber. To achieve the objects of the present invention, the surface of the object to be simulated (e.g., a slab or an individual shoe sole) is coated with silicone rubber casting HFM-45 and hardener No. 1 in a weight ratio of about 10 to 1. both
It has been found that a good cured molding surface can be obtained when coated with a mixture of the This type meets the above requirements and can also be reinforced on the outside if necessary. The molds used when a blowing agent is present in the formulation are the same as when molding is carried out without a blowing agent. However, when a blowing agent is used, the mold used must be strong enough to withstand the pressure of gaseous decomposition products generated from the blowing agent during the molding operation. If a silicone rubber mold is used, it may be reinforced with an intermediate layer of a suitable reinforcing material (eg glass fiber). In the above mold surface molding method using a foaming agent, an appropriate space is created in the mold and the mold product expands to form a microporous interior (a relatively thick, essentially non-porous (surrounded by epidermis or wall)
It is necessary to be able to obtain With respect to the molding compositions described herein and the use of blowing agents also described herein, a mold is filled with the molding mixture in the range of about 80 to about 90% and then molded as described above in a closed mold. When subjected to the conditions, a mold product with the desired physical appearance is obtained. The block copolymer plastomers of this invention may optionally be mixed with up to about 60 parts naphthenic oil per 100 parts block copolymer. It is also contemplated that up to about 30% by weight of chemically related block and random copolymers (e.g. elastomers or plastomers) may be substituted for the plastomers described above to adjust, for example, mold flow and stiffness of the final composition. It is within the scope of the invention. Microwave frequency as used in the present invention means about 25 to about 120 MHz (megahertz). Molded samples are also produced using a Compo Industries, Inc. J-type machine with a power output of 10 kilowatts at 40 MHz. Example 1 Ingredients are mixed in a Banbury mixer at approximately 280〓 (138
A series of compositions are prepared by mixing for 6 minutes at a temperature of Grate each composition from a mixer at about 250°C (121°C) to form pellets. Table A shows the formulations used in parts by weight.

【table】

[Table] Add an appropriate amount of each ingredient into pellets at room temperature.
Pour into an inch x 6 inch (15cm x 15cm) mold. Cavity depth averages approximately 1/3 inch (0.8 cm)
shall be. Each filled mold is covered with a paper release sheet and the set is placed into a commercial molding machine that uses microwave energy as the heating medium. Approximately 40 psig when the upper molding plate is lowered
(280Kpa gauge) pressure to cover the mold.
Upon contact with the paper, the microwave unit is energized to preheat the composition. After 3 to 6 seconds the pressure will automatically increase to 120psi and hold for 25 seconds until the temperature of 300㎓ is reached. Turn off the microwave field and cool one set while leaving it in the press or transfer it to another press to cool it [circulating cooling water at about 50 °C (10 °C) between the plates]
The period of time for cooling one set in contact with Plato is approximately 2
minutes]. Open the press and remove the product from the mold at approximately 120°C (49°C). The preheating times used and the results obtained are recorded either in Table B or in the notes.

[Table] Comparison of the physical properties of a sample obtained by flow molding a representative dense composition exemplified as Composition A with the physical properties of a sample compression molded from a representative cultivated crepe rubber at the same temperature. do. Although the two molded samples look similar, it is immediately apparent that the synthetic product is stronger and more abrasion resistant than the unvulcanized naturally grown crepe rubber. The obtained surface resistivities also show that synthetic crepe rubber attracts less dirt and dust than natural materials. A value of 10 ⁵ ohms for the natural material indicates that the static charge dissipates gradually, whereas a value of 10 ¹⁰ ohms for composition A indicates that the static charge dissipates quickly (e.g. within a few seconds or less). It is shown that. The suture resistance of a sample molded from Composition B is compared with a sample molded from naturally grown crepe rubber. Approximately 1/4 inch (0.6
cm) formed sheets using an Instron test machine (Instron
Corp., Canton, OH) on a horizontally slotted board. Stitch the sample with thread exactly 1/4 inch apart, passing the ends of the thread through the slots in the board. Next, clip the end of the thread to the clasp at the bottom of the Instron machine. Even if a tensile test is performed after this, the sample does not deform. The results are described below.

[Table] This result shows that the suture resistance of dense synthetic crepe rubber is superior to that of natural products. Several samples of microporous Composition C are tested for NBS abrasion resistance. One sample is
One shows a value of 11% of RMA, and the other shows a value of 11% of RMA.
It is 15%. That is, on average, it is 13% of RMA. This value is somewhat inferior to that of naturally grown crepe, which has an RMA of 27%. However, natural materials do not have foam structures. Example A Mold structure Make two types of silicone rubber molds. One shoe sole can be molded from one side, and a slab can be molded from the other. For each, attach the prototype (e.g. crepe rubber sole or crepe rubber slab) to a horizontal glass.
Surround it with a piece of polyurethane foam about 1/4 inch (0.6 cm) higher than the highest point of the model. The horizontal distance between the master pattern and the polyurethane strip may range from about 1/2 inch (1.3 cm) to any reasonable distance, such as about 2-3 inches (5-7.6 cm).
Finally, a metal spacer rail approximately the same height as the polyurethane strip is passed around the polyurethane strip to support the flat metal plate and adjust the thickness of the mold. A thin layer of Vaseline is then applied as a release coat to the master, any exposed glass surfaces, and the bottom of the cover plate. Liquid silicone rubber composition (10 parts by weight of HFM-45 and 1 part by weight of its curing agent, both from Compo Industries, Inc., Waltham,
(commercially available from Mass.) for approximately 2 minutes, and the mixture is degassed in a vacuum chamber to remove substantially any air or gas present. Pour a small amount of this degassed mixture onto the pattern and rub to make good contact and remove any trapped air. Then pour enough of the degassed mixture into the mold to sufficiently cover the pattern. about
After 15 minutes, cut a fiberglass screen (such as that used for screen windows) to size and place it on top of the rubber compound in the mold. The mold is then filled with the degassed mixture, and excess rubber compound is drawn out by placing a cover over the mold and weighting it so that it rests properly on the metal rails. Next, after curing this at room temperature for an appropriate period of time (approximately 48 hours), the weight is removed. As a finishing touch, vent holes approximately 1/64 inch in diameter are drilled in appropriate locations in each silicone rubber mold to vent air trapped during casting, as is known in the art. The size of the crepe rubber sole chosen as one of the prototypes is 7-1/2. The original size of the slab is 9
x 13 inches (23 x 33 cm). The original thickness of the slab averages approximately 3/8 inch (0.9 cm). The original size of the sole is approximately 1 inch (2.5cm) at the heel and approximately 5/16 at the bottom.
inch (0.8cm). B. Manufacture of Soles by Flow Molding The microporous composition described in Table A is used to fill approximately 80 to 90% of the cavities of each mold. Although particulate compositions are also used in this example, it is often desirable to form such compositions into sheets. This is because a material plate of suitable dimensions is obtained for placement in the mold. Each composition is shaped as described above. The bottom and sides of the sole obtained from each sole mold have the appearance and texture of crepe rubber. Punch out soles from slab products. The bottom of the slab has the look and feel of crepe rubber, and the cut surface is relatively smooth in appearance. However, it is possible to use the above-mentioned punched products whose cut surfaces are scored or corregated to resemble the appearance of crepe rubber. The specific gravity of the flow-molded prototype is approximately 0.8.

Claims (1)

[Scope of Claims] 1. A method for producing a molded article having at least one surface imitating the appearance of naturally grown crepe rubber, comprising: (i) a styrene/butadiene linear or radical block copolymer (the content of polymerized styrene is about 20 to about 50% by weight of the total block copolymer) and resinous polymers of vinyl-substituted aromatic compounds (about 20% to about 50% by weight of the total block copolymer)
10 to about 60 parts of alkylene glycols and mono- or di-alkyl thereof, in an amount sufficient to rapidly heat the composition using microwave frequency energy. (ii) blending said composition with a polarizing agent selected from ether, ethanolamine, isopropanolamine and their hydrocarbyl-substituted derivatives and mixtures thereof, and optionally dispersing a blowing agent throughout the composition; (iii) closing the mold; (iv) melting said composition using microwave energy; and (v) melting said composition using microwave energy. under molding conditions, and (vi) removing the resulting molded article from the mold. 2. In the method described in item 1 above, the blowing agent is activated by increasing the temperature during the molding process, and the amount of the blowing agent-containing composition charged into the mold is reduced from the activated blowing agent. A method in which the expansion of the composition due to the evolution of gas is such that it results in a microporous structure within the epidermis of a normal dense polymer. 3. A method according to item 2 above, in which the composition containing a blowing agent is placed into the mold in an amount that fills about 80% to about 90% of the mold. 4. In the method described in paragraph 2 or 3 above, the amount of blowing agent is from about 0.5 to about 0.5 of the total polymer mixture.
How to be 10php. 5 In the method described in any of the above items,
A method wherein at least one surface of said mold is in the shape of a naturally grown crepe rubber mold. 6 In the method described in any of the above items,
A method of effecting melting by subjecting the composition to microwave energy in the range of about 25 to about 120 MHz (megahertz) for a period of time in the range of about 4 seconds to about 4 minutes. 7 In the method described in any of the above items,
A method in which, after melting the mixed composition, sufficient pressure is applied on a closed mold for a period sufficient to form a molded article in the mold. 8 In the method described in any of the above items,
A method in which said mixed composition also contains perfumes, pigments and/or fillers.