METHOD OF MANUFACTURE OF THERMOPLASTIC ELASTOMER COMPOSITIONS

Abstract: (A) polypropylene (10-90 weight part), (B) halogenated butyl rubber (90-10 weight part, (A) + (B) = 100 weight part), (C) olefinic rubber (10-120 weight part) and (D) mineral oil softening agent (5-120 weight part) are heated in the presence of (E) metal oxide and/or metal chloride. To 100 weight part of the resulting composition are added, (F) polyolefin (100-600 weight part) and (G) vulcanizable olefinic rubber (50-500 weight part) and the components are mixed and heated in the presence of (H) organic peroxide. The resulting thermoplastic elastomer composition has good paintability, moldability, compatibility, low temperature impact strength, and especially high stiffness at elevated temperature.

Description: "METHOD OF MANUFACTURE OF THEEMOPLASTIC ELASTOMER COMPOSITIONS" BACKGROUND OF THE INVENTION This invention is concerned with a method of manu¬ facture of a partially crosslinked olefinic thermoplastic elastomer (TPE) compositions. Although compounds comprising a polyolefin and a partially crosslinked rubber possess good properties as TPEs such as heat resistance, mechanical strength, flexibility, and elasticity, their flow properties are inferior to those of common plastics, and this has limited their use in large molded parts owing to problems such as "flow marks." To improve these problems, for example, Japanese Patent 54-23702 teaches the use of compounds consisting of poly¬ olefin and two types of rubber, partially crosslinked, and Japanese Patent 56-15743 teaches a compound in which a poly¬ olefin is blended with a polyolefin/rubber blend that has been treated with organic peroxides. Also Japanese Patent 56-15740 teaches the methods of manufacture of such com¬ pounds. Japanese Application 60-188419 discloses compositions in which the rubber phase includes a halobutyl rubber, which is vulcanized with metal oxides (MOx) and/or Metal Chlorides (MCI) and partially crosslinked in the presence of a poly¬ olefin, and then additional polyolefin is added. Although such TPE compounds have excellent properties such as processabilit , low temperature impact, paint- ability, flexibility, and mechanical strength, their stiff¬ ness at elevated temperatures was less than adequate com¬ pared to polyurethane elastomers. It is one object of the present invention to improve high temperature stiffness of this type of TPE, without loss in the characteristics of olefinic TPEs. SUMMARY OF THE INVENTION A method of manufacture of compositions in which polyolefin and a rubber phase comprising halobutyl rubber is partially crosslinked using MOx and/or MCI and are com¬ pounded further with a vulcanizable olefinic rubber, which is then crosslinked using organic peroxides. Thus, a blend of (A) polypropylene 10-90 weight parts (pts.), (B) halobutyl rubber 90-10 pts. (wherein (A) + (B) = 100 pts.), (C) olefinic rubber 10-120 pts., and (D) mineral oil softening agent 5-120 pts. are thermally treated with (E) MOx and/or MCI to crosslink the halobutyl rubber, to which blend of 100 pts. are then added, (F) polyolefin 100-600 pts., and (G) vulcanizable olefinic rubber 50-500 pts., which is then thermally treated with (H) an organic peroxide to crosslink the olefinic rubber. DETAILED DESCRIPTION (A) Polypropylene (PP) PP suitable for use in this invention includes homo- polymer or copoly er with ethylene, 1-butene, 1-pentene, 1-hexene or 4-methylpentene or other alpha-olefins with propylene as the main component, including random or block copoly ers. Melt flow rate (MFR) is about 0.3-60 g/10 min, preferably 1-40, most preferably 3-30. Component A of the composition has the highest melting point of polyolefins, and imparts heat resistance and improved mechanical proper¬ ties to the compound. (B) Halobutyl Rubber For purposes of this invention halobutyl rubber means halogenated butyl rubber. The halogen can be chlorine or bromine, usual content is 0.5-4.0 wt%. It is preferable that this component has a Mooney Viscosity, ML 1 + 8 (100°C) of about 30-100 and 0.5-4.0 mol% unsaturation. Halobutyl rubber can be crosslinked using MOx and/or MCI," and exists as a dispersed crosslinked rubber phase, imparting abrasion resistance, impermeability and "anti-slip properties" to the compound. (C) Olefinic Rubber Rubber in which two or more of: ethylene, propylene, butene, 1-hexene, 4-methyl-l-pentene, etc. are copolymerized (e.g., ethylene propylene rubber, EPR) or rubber in which two of the above monomers (preferably ethylene and propy¬ lene) are polymerized with dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene-norbornene or ethylidenenorbornene (ENB) or conjugated dienes such as butadiene or isoprene. The preferred olefinic rubber has Mooney Viscosity, ML 1 + 8 (127°), of 5-300, Iodine Value up to 30, and 35-85 wt% ethy¬ lene content. Such olefinic rubber may be polyisobutylene, butyl rubber, etc. The olefinic rubber is present in the compound as a non-crosslinked rubber, and imparts flexibility, flowability and also acts as a binder at the interface of (A) and (B), improving tensile strength and elongation. (D) Mineral Oil Softener Suitable materials include hydrocarbon petroleum fraction which lessens the hardness of vulcanized rubber. Included are paraffinic, naphthenic, and aromatic types. Among these, aromatic oils have a detrimental effect on paintability, and are unsuitable for use in materials which will be painted. (E) Vulcanizing Agents Metal oxides ( MOx ) includ ing z inc oxide , magnesium oxide, lead oxide, calcium ox ide , etc . , but z inc ox ide is preferred . Among metal chlor ides ( MCI ) are zinc chloride and stannic chloride. It is also desirable to use magnesium oxide as an accelerator, to avoid corrosion of molds due to generation free halogen. The amount ' of vulcani z ing agents relative to 100 parts of ( A ) + ( B ) + ( C ) + ( D ) should be about 0.2-10 parts, preferable 1 to 5 parts . (F) Polyolefin Polyolefin useful in this invention include homo- or copolymers of two or more of ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-l-pentene, or copolymers of vinyl esters, unsaturated carboxylic acids or their deriva¬ tives with any of the above. Random or block copolymers are encompassed. Melt flow rate, MFR (at 190°C, but 230°C for propylene-based polymers) should be in the range of about 0.1-20 g/10 min. for ethylene-based and about 15-60 g/10 in. for propylene-based polymers. Also, two or more of the above polyolefins may be combined. Preferred among the above are low density polyethylene (LDPE), linear low den¬ sity polyethylene (LLDPE), medium-density polyethylene (PE) or high density polyethylene (HOPE), polypropylene (PP), or random or block copolymers with propylene as the major com¬ ponent. The presence of polyolefin improves the flowability or paintability of the compounds of the present invention without detriment to rubber elasticity. Since (F) and (A) have a similar function, these components can be added in various ratios. However, the beneficial effect of (F) is particularly observed when it is used with the previously dynamically vulcanized blend of (A)-(D) (in other words heat treated with mixing in the presence of vulcanizing agents). (G) Vulcanizable Olefinic Rubber Useful materials include olefinic rubber which can be crosslinked through mixing and heating to decrease or elimi¬ nate flow of the rubber. For example, ethylene propylene (EP) copolymer rubber (EPR), ethylene-butadiene copolymer rubber, ethylene-nonconjugated diene copolymer rubber, etc. are included. Among these, EPR and EP-ENB (ethylidene norbornene) rubber are preferred. The vulcanizable rubber should have a Mooney Viscosity of ML 1 + 8 (127°C) of about 5-300 and an iodine value of less than 30. In the final composition, the vulcanizable olefinic rubber is present as a partially crosslinked rubber phase, improving stiffness at elevated temperature. (H) Organic Peroxides The organic peroxides useful for crosslinking of the olefinic rubber are those with a half-life decomposition temperature of 160-220°C; for example di-t-butyl peroxide, dicumyl peroxide, benzoylperoxide, 2,5-dimethyl-2,5-di- (t-butyl peroxy) hexane-3, 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane. In addition, for the treatment with per¬ oxide, it is desirable to use an accelerator such as p,p'- dibenzoylquinone dioxime. The organic peroxide is used to partially crosslink the composition of the vulcanizate treated with (E) together with the polyolefin and the vul¬ canizable olefinic rubber, giving improved high temperature stiffness. The accelerator is included for the purpose of carrying out the partial crosslinking reaction smoothly and uniformly. (I) Other (Optional) Components As necessary for the particular end use, other optional components can be added to the composition includ¬ ing oil-resistance enhancing nitrile rubbers or other syn¬ thetic or natural rubbers. Also, modified polyolefins reacted with unsaturated carboxylic acids or their deriva¬ tives, e.g., aleic anhydride, endo-bicyclo-( 2 ,2 ,1 )-5-hep- tene-2 ,5-dicarboxylic anhydride may be incorporated. Other components such as antioxidants, UV absorbers, metal aging retardants, antistatic agents, lubricating agents, electri¬ cal property improvers, process aids, flame-retardants or coloring agents and inorganic fillers such as talc, barium sulfate, mica, and calcium silicate fillers may be added as required. These may be added at any stage of the manufactur¬ ing process. Ratios of Components Ingredients are expressed on the basis of weight parts. The ratios of (A), (B), (C), (D), (E) are: (A) 10-90 pts., preferably 20-70 pts.; (B) 10-90 pts., preferably 30-80 pts.; with (A) + (B) = 100; (C) 10-120 pts., preferably 10-100 pts., (D) 5-120 pts., preferably 5-100 pts. Also, the incorporation of (D) in the Second Stage (to be defined below) is desirably 1-60 pts. (E) The crosslinking agent should be used at 0.2-10 pts., preferably 1-5 pts., relative to 100 pts. of (A)-(D). When (A) is less than 10 pts., the compounds lose mechanical strength and heat resistance is poor. When (A) is greater than 90 pts., hardness and compression set are high and elastomeric properties are lost. When (C) is less than 10 pts., flexibility is low and flowability is poor. In addition, the compatibilization of (A) and (B) becomes poor. On the other hand, when (C) is greater than 120 pts., mechanical strength decreases and compression set increases. When (D) is less than 5 pts., flexibility is inade¬ quate and when (D) is greater than 120 pts., paintability becomes poor, mechanical strength decreases and the com¬ pounds become sticky. The amounts of components (F) and (G) to be used with 100 pts. of the vulcanizate crosslinked with (E) are: (F) 100-600 pts., preferably 200-500, and (G) 50-500 pts., pre¬ ferably 60-400 pts. The amount of (H) (organic peroxide) relative to 100 pts. of the partial vulcanizate (A-E) + (F) + (G) is: 0.005-1 pt., preferably 0.01-0.3 pts. The accelerator should be used at a level of 0.005-1 pt., pre¬ ferably 0.01-0.4 pts. When (F) is less than 100, flow- ability and paintability are inadequate, while if (F) is greater than 600 pts., the flexibility and rubbery proper¬ ties of the composition are lost. When (G) is less than 50 pts., flexibility and molding flowability are low, and in addition compatibilization with the partial vulcanizate from (E) is poor. On the other hand, when (G) is greater than 500 pts., mechanical properties decrease and compression set becomes large. When the amount of (H) is less than the above-mentioned lower bound, the crosslinking of the vulcan¬ izable rubber is inadequate and good high temperature stiff¬ ness is not obtained. When (H) exceeds the high end of the range, the flowability of the compound decreases as the degree of crosslinking increases. It is not desirable for the accelerator to exceed the mentioned range because the crosslinking reaction proceeds too far, resulting in low flowability, and in addition unreacted agent remains in the compound, changing its physical properties. The amounts of the other components should desirably be in the range 0-30 wt%. Method of Manufacturing the Composition First, (A), (B), (C), (D), and vulcanizing agent (E) (MOx and/or MCI), and other components as necessary, are mixed and thermally treated, i.e. blended in the melt. The blending should be done at a temperature at which all com¬ ponents melt/flow, usually 160-250°C and desirably 170-220°C for 1-10 min., desirably 3-5 min. In this way, a composi¬ tion in which the dispersed component (B) only is selec¬ tively crosslinked is obtained. The melt blending may be carried out in equipment such as pressure kneaders, Banbury Mixers, screw-type ex¬ truders, etc. (This operation is referred to as the First Stage. ) Next, (F), (G) and (H) (organic peroxide plus accel¬ erator) are added to the blend and melt blending is carried out. For example, pellets of the above components can be premixed in a Henschel mixer, ribbon blender, etc., then melt blended in an extruder, Banbury or kneader, etc. At this time, various stabilizers, coloring agents, inorganic fillers, softening agents, etc. can be added as required. (This is referred to as the Second Stage). In the composition produced by the method of this invention, (B) is partially crosslinked, so compatibility is excellent, and without loss of rubbery properties, the mechanical strength is high, and impact strength, especially at low temperature, is improved. In addition, due to the successive vulcanization with components (F) and (G), and the uniform incorporation of (I), heat resistance, paint¬ ability adhesion, flowability and gloss are improved. Thus, there are no flow marks in large molded parts, and products have good high quality gloss. The composition of the present invention can be processed easily using conven¬ tional techniques for TPEs, such as blow molding, extrusion or injection molding, etc. The compounds of the present invention have excellent processability and a good balance of flexibility, strength, and heat resistance. Hence, they are especially suitable for use as materials for auto parts, such as rack and pinion boots, hoses, side moldings, spoilers, and bumpers. EXAMPLES Test Methods (1) MFR: JIS K7210 (wt. 2.16 kg, 230°C). (2) MI: JIS K7210 (wt. 2.16 kg, 190°C) . (3) Tensile strength and elongation at break: JIS K7113. (4) Bending modulus: JIS K7203. (5) Izod impact: JIS K7110. (6) Gloss: JIS K7105, measured on 60° plane. (7) Heat deflection temperature: JIS K7207. (8) Processability: (a) Conditions Inj. molder: Mitsubishi Natco 350 MV XL40 Inj. molding temperature: 230°C Inj. molding pressure: primary 800 kg/cm^ Inj. molding pressure: secondary 500 kg/c ^ Inj. time: 13 seconds Cycle: 38 seconds Gate: ride gate Part: 3 x 100 x 350 mm flat plate (b) Judgement Flow-marks 0: none Flow-marks D: very little Flow-marks X: many, severe (9) Paintability: (a) Primer method After test piece was cleaned in tri- chloroethylene (TCE) vapor for one minute, primer ( "Pla-gloss, " Nippon Yushi Co.) was painted and treated at 120°C for 30 min¬ utes. Then, over this layer was painted upper coating ("Flexene 101," Nippon Paint Co.), and treated at 120°C for 30 minutes. (b) Plasma method After test piece was cleaned in TCE vapor for one minute, it was plasma treated (O2 plasma, 1.0 KW x 1.0 torr x 60 seconds) and painted with an upper coating ("Flexene 101," Nippon Paint Co.), and treated at 120°C for 30 minutes. (c) Evaluation Initial adhesion: according to JIS K5400 test, "tile." Resistance to warm water: Appearance and "tile" test after immersion in 40°C water for 240 hrs. (10) Gel Fraction: One g. of sample was placed in a 100 mesh gold screen and boiled in hot xylene for 12 hours. Then, gel fraction was determined as the remaining xylene insolubles after vacuum drying for 24 hours. Examples 1-14, Comparative Examples (Comp. Ex.) 1, 2. Materials used Component (A) Propylene-ethylene block copolymer (MFR = 15.0 g/10 min., ethylene 7 wt%), referred to as "PP-Block-1." (B) Chlorobutyl rubber (ML 1 + 8 (100) = 50, chlorine content 1%, 2 mol% unsat.), referred to as "CIIR." (C) ENB-EPDM (ML 1 + 8 (127) = 35. Iodine Valve = 4.0, ethylene = 65 wt%), referred to as "EPDM-1." (D) Naphthenic process oil (viscosity - specific gravity coefficient = 0.880), referred to as "softener." (E) ZnO, MgO (halogen accelerator). (F) Propylene-ethylene block copolymer, (MFR = 40 g/10 min., ethylene content 7%), referred to as "PP-Block-2". (G) ENB-EPDM (ML 1 + 8 (127°C) = 45, Iodine Valve = 3, referred to as B EPDM-2 π ), EPR (ML 1 + 4 (100°C) = 24, ethylene content = 73%, referred to as "EPR"). (H) Organic peroxide (Nippon Yushi Co., "Perhexyne 2,5B"), P,P'-dibenzoylquinone dioxi e (acceler¬ ator) . Other: Talc (silane treated, avg. dia. 2.5 microns), EPDM rubber, (ML 1 + 8 (127) = 45, iodine value = 3, ethylene = 65 wt%), referred to as "EPDM-2"); EPR (ML 1 + 4 (100) = 24, ethylene 73 wt%), referred to as "EPR", MA - modified pro¬ pylene-ethylene block copolymer (MA content 0.5 wt%), referred to as "CMPP"; acrylonitrile-buta- diene rubber (ML 1 + 4 (100) = 56, AN content = 35%), referred to as "NBR". Preparation of the Composition (A)-(D) and talc were combined in the proportions shown in Table 1, and to 100 pts. of the resulting composi¬ tion 2 pts. zinc oxide (ZnO) and 0.5 pt. magnesium oxide (MgO) were added and melt blended in a Banbury Mixer at 170°C for 3 minutes. The resulting composition was sheeted, cut, and pelletizied (Stage 1). Next, to the pellets obtained in Stage 1 were added (F), (G), NBR, CMPP, and softening agent, in the proprotions shown in Table 1. To 100 pts. of this blend were added 0.1-0.3 pts. of organic peroxide and 0.12-0.36 pts. of vul¬ canization accelerator, premixing in a Henschel mixer and extruding in a twin-screw extruder at 200°C to obtain the final product of the invention. The characteristics of each compound are shown in Table 1. In addition, the paintability properties, both initial adhesion and warm water resistance were good at 100/100. For comparison. Table 1 also shows properties of Compounds (comparative examples) where the vulcanizate from Stage 1 was blended with PP-Block-2 and EPR or EPDM and thermally treated as in Example 1 in the absence of organic peroxide (see table). Table 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 • Ex. 6 Ex. 7 Ex . 8 Ex. 9 Ex. 10 Ex . 11 PP-Block-1 (pts.) 50 50 50 50 50 50 50 50 50 50 50 CIIR 50 50 50 50 50 50 50 50 50 50 50 EPOM-1 100 100 100 100 100 100 100 100 100 100 100 Softener 94 94 94 94 94 94 94 94 94 94 94 Talc 19 19 19 19 19 19 19 19 19 19 19 Stage 2 PP-Block-2 (pts. ) 700 700 400 400 700 700 700 700 1 , 565 1 , 565 700 HDPE LLDPE 300 300 EPR EPDM-2 EPR EPR EPR EPR EPR EPR EPR EPR EPR 200 875 EPDM-2 EPDM-2 400 400 400 400 . ~ ~ ~ 400 400 400 375 1,250 200 Softening Agent (pts.) 5 5 5 5 5 __-_. 5 5 5 5 5 NBR 200 Org. Peroxide (pts.) 0.3 0.3 0.3 0.3 0.3 0.3 0.2 0.1 0.3 0.3 0. 3 J Accel. (pts.) 0.36 0.36 0.36 0.36 0.36 0.36 0.24 0.12 0.36 0.36 0. 36 Fundamental Properties MFR (g/10 min. ) 10 15 14 12 Flex. Mod. (kg/cm 2 ) $ 23"C 2,800 3,000 3,000 3,100 3,000 2,800 2,800 2,900 2,800 2,900 3,100 e 80° 1,150 1,200 1,180 1,080 1,170 1,140 1,050 1,000 1,140 1,180 1,250 Tens. <a Break (kg/cm 2 ) ) 110 130 130 125 130 115 85 87 95 105 112 Elong. @ Break (%) 300+ 300+ 300+ 300+ 300+ 300+ 120 130 300+ 300+ 300+ Room Temp. IZOD NB NB NB NB NB NB NB NB NB NB NB (kg-cm/c ) (* -40°C 55 65 62 75 65 52 45 46 65 63 57 Heat Distort. Temp. (° °CC)) 60 62 63 62 62 60 55 55 60 61 60 Gel Fraction %) 36 38 42 40 38 38 25 20 35 38 33 Proceasabi1ity Flow Marks 0 0 0 0 0 0 0 0 0 0 0 Gloss (») 32 30 35 40 32 30 33 35 40 40 34 Paintability Primer Method 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 Pl asma Metliod 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 NB - No ϊrealc . Table 1 (Continued) Comparative Ex. Ex. 12 Ex. 13 Ex. 14 1 2 PP-Block-1 (pts.) 50 60 40 50 50 CIIR " M 50 40 60 50 50 EPDM-1 " " 100 110 100 100 100 Softener " " 94 94 94 94 94 Talc " " 19 * 19 19 19 Stage 2 PP-Block-2 (pts.) 700 700 700 700 700 EPR EPR EPR EPR EPDM-2 400 400 400 400 400 Softening Agent " " 5 5 5 CMPP 2 Org. Peroxide " " 0.3 0.3 0.3 Accel. " " 0.36 0.36 0.36 Fundamental Properties Ln MFR (g/10 min.) I Flex. Mod. (kg/cm 2 ) g 23°C 3,000 2, ,900 2 ,900 3,400 3,200 § 80° 1,200 1 ,190 1 ,150 890 840 Tens, θ Break (kg/cm 2 ) 120 115 109 98 102 Elong. θ Break (%) 300+ 300+ 300+ 300+ 300+ Room Temp. IZOD NB NB NB NB NB (kg-cm/cm) @ -40"C 61 52 59 35 40 Heat Distort. Temp. (°C) 60 62 58 50 52 Gel Fraction 35 28 38 55 58 Processability Flow Marks 0 0 0 0 0 Gloss (%) 38 36 30 35 33 Paintability Primer Method 100/100 100/100 100/100 100/100 100/100 Plasma Method 100/100 100/100 100/100 100/100 100/100 NB « No Break .

Claims: CLAIMS What is claimed is: 1. A method of manufacture of thermoplastic elastomer comprising thermally blending (A) pro¬ pylene 10-90 weight part, (B) halogenated butyl rubber 90-10 weight part, wherein (A) + (B) = 100 weight part, (C) olefinic rubber 10-120 weight part in the presence of (E) metal oxide and/or metal chloride, and to 100 weight part of the resulting composition are added (F) polyolefin 100-600 weight part and (G) vulcanizable olefinic rubber 50-500 weight part and said components (A) through (G) are further mixed and heated in the presence of (H) organic peroxide.

Inventors: BABA ISAO, KANAI TSUYOSHI, KOMATSU MASATO, NARUKAWA KIYOTADA, YAMAMOTO NOBORU, BABA, ISAO, KANAI, TSUYOSHI, KOMATSU, MASATO, NARUKAWA, KIYOTADA, YAMAMOTO, NOBORU
Applicants: TOA NENRYO KOGYO KK, TOA NENRYO KOGYO K.K.
Application year: 1987
Main classification: C08L9
IPC codes: C08K3, C08K5, C08L1, C08L7, C08L21, C08L23, C08L27, C08L33, C08L51, C08L53, C08L77, C08L101