JPS63142032A - Production of exterior automotive trim part - Google Patents

Abstract

PURPOSE:To obtain the titled parts having excellent low-temperature impact, heat resistance, appearance, etc., by dynamically heat-treating a mixture of a specific crosslinkable type rubber, a decomposition type olefinic resin and a softener for rubber in a specific ratio in the presence of an organic peroxide and molding the mixture. CONSTITUTION:A mixture of (A) 10-35wt% peroxide crosslinkable type rubber which has Mooney viscosity of ML1+4(100 deg.C)10-ML1+8(120 deg.C)300, <=30 iodine value and 25-50wt% propylene content, (B) 60-70wt% peroxide decomposition type olefinic resin having 0.1-50g/10min melt flow rate and (C) 5-25wt% softener for rubber is dynamically heat-treated in the presence of an organic peroxide by kneading in molten state, etc., to give a thermoplastic resin composition having 2,000-4,500kg/cm<2> modulus in flexure. Then the composition is molded to give the aimed exterior automotive trim parts.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an automobile comprising a partially crosslinked olefinic thermoplastic resin composition having appropriate flexibility and excellent moldability. This relates to a method for manufacturing exterior parts.

[Conventional technology]

In recent years, the use of plastic for automobile exterior parts has progressed rapidly.
Various plastic materials are now being used not only for moldings, lamp housings, front grilles, mudguards, side bumpers, etc., but also for bumpers, fascias, bodies (parts), etc. that were previously made of metal.

Examples of plastics include polymer alloy materials such as RIM-urethane, composite polypropylene, and polycarbonate/ABS.

In particular, there are two types of bumpers: a low-rigidity type that absorbs energy through deformation during a collision and has recovery characteristics, and a high-rigidity type that has inferior deformation recovery performance but is lightweight and inexpensive.The former uses RIM-urethane, Partially crosslinked ethylene-propylene rubber (EP rubber) compounded polypropylene (
P, P), etc. with elastic modulus of 2000 to 4500 kg/cJ
The latter is made of EP rubber and inorganic filler-blended polypropylene (
PP) etc., the elastic modulus is generally 6,000 to 12,000 kg/cJ.

For low-rigidity types, RIM-urethane has traditionally been the mainstream in terms of deformation recovery and moldability for large parts, but recently, partially crosslinked EP rubber compounded PP has improved paintability and deformation recovery. Recently, RI has become popular due to its material cost advantages and the ability to automate the manufacturing process using general-purpose injection molding.
It is enough to replace M urethane.

Partially crosslinked EP rubber compounded PP (commonly called olefinic thermoplastic elastomer when the P2O content is 50% or less) has already been disclosed in JP-A-48-26838 (EP rubber/PP = 60 to 80/40). ~20% by weight partially crosslinked thermoplastic elastomer), Japanese Patent Publication No. 1127-1983
Publication No. 29 (EP rubber/PP-40~90/60~10
Method for producing partially crosslinked thermoplastic elastomer (parts by weight),
Publication No. 59-30736 (EP rubber/PP=40-9
0/IQ to 60% by weight and a method for producing a thermoplastic elastomer by further adding other rubber or a rubber softener),
No. 56, -15740 (EP rubber/PP=50~
A partially crosslinked thermoplastic elastomer is prepared by adding other rubbers and rubber softeners to 10,070 to 50 parts by weight, and 10 to 100 parts by weight per 100 parts by weight of this elastomer.
Method for producing thermoplastic elastomer by adding part by weight of PP), Publication No. 56-15743 (EP rubber/PP
=50~90150~10 parts by weight are further added with other rubbers and rubber softeners to make a partially crosslinked elastomer, and this elastomer/PP=5~50150~95 PP is added at a ratio of 4% by weight. thermoplastic resin composition)
etc. are publicly known.

[Problem that the invention seeks to solve]

However, the elastic modulus 2 obtained from these conventional techniques
000 to 4,500 kg/Cr1 low-rigidity type bumper materials never had a good quality balance in terms of low-temperature impact, heat resistance, molded product appearance (flow marks, sink marks, etc.), molding cycles, etc.

Especially, Special Publication No. 56-15740 and No. 56-1574.
Compositions obtained by the method described in Publication No. 3, in which a partially crosslinked composition is first slowly added and diluted with a resin component, have a slow plasticization speed during molding, resulting in poor molded appearance such as sink marks. It was easy.

c. Means for Solving Problems] The inventors of the present invention further studied the formulation and manufacturing method to satisfy the above quality balance, and as a result, the inventors of the present invention determined that a large amount of peroxide-decomposed polyolefin resin of 60 to 70% by weight was used. Used in the range, and Japanese Patent Publication No. 56-15740, No. 56-1
Rather than adding PP to a partially crosslinked thermoplastic elastomer as in the technique described in No. 5743, the entire amount is dynamically heat treated in the presence of an organic peroxide together with a peroxide crosslinked rubber and a rubber softener. As a result, the present invention was completed by discovering a thermoplastic resin composition having an excellent quality balance in low-temperature impact, heat resistance, molded product appearance, and molding cycle.

That is, the present invention dynamically heat-treats a mixture of rubber, resin, and rubber softener in the presence of an organic peroxide to form a partially crosslinked thermoplastic resin composition, and then In the method of molding this into an automobile exterior part by a conventional method, each of the following components A to C is used as a compounding component of the mixture, and the bending elasticity of the thermoplastic resin composition is rate is 200
This is a method for producing vehicle exterior parts, characterized in that the weight is in the range of 0 to 4500 kg/-.

Component A: Mooney viscosity is M L , 4 (100'C)
] O~ML++++ (120'c) 300, peroxide crosslinked rubber with iodine of 30 or less and propylene content of 25~50% by weight 10~35% by weight Component B: Melt flow rate of o, i~50g/10
Peroxide decomposition type olefin resin 60-70% by weight Component C: Rubber softener 5-25% by weight [Function] The peroxide crosslinked rubber of component A used in the present invention is, for example, ethylene/propylene. Copolymer rubber (E
PM), an elastomer of an amorphous random copolymer mainly composed of olefins, such as ethylene propylene non-conjugated diene copolymer rubber (EPDM), which is produced by heat treatment in the presence of organic peroxide. Mainly a crosslinking reaction occurs, resulting in a decrease in flowability. In particular, the above two types of rubbers are preferred, and in this case, dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylnorbornene, ethylidenenorbornene, etc. are used as the nonconjugated diene.

Among these, EPDM, especially ethylene-propylene-ethylidene norbornene copolymer rubber, is preferred since it provides a suitable crosslinked structure.

The Mooney viscosity of these rubbers is ML, or (100"C
) to ~Ml-+-e (120°C) 300, preferably M L +-tc 100°C) 40-ML. , (1
20°C) 250.

If a Mooney viscosity is less than this range, the resulting molded product will have poor low-temperature impact strength, and if it exceeds this range, the molding processability will be poor, especially the appearance of the molded product. Getting worse.

There is no particular problem as long as the iodination (unsaturation degree) of component A used is within the range of 30 or less.

The propylene content in this component is generally 25 to 50 kg by weight; if the propylene content is less than this range, the resulting molded product will have poor low-temperature impact strength, and if it exceeds this range, the molded product will not tack. This deteriorates and mold release properties become a problem.

The blending ratio of this component is 10 to 35% by weight, preferably 15 to 30% by weight, based on the total amount of component A and components B and C to be described later. If it is less than this range, the low-temperature impact will worsen, and if it exceeds this range, the appearance of the resulting molded product will be significantly deteriorated.

Next, the peroxide-decomposed polyolefin resin of component B used in the present invention is thermally decomposed by heat treatment in the presence of peroxide to reduce its molecular weight and increase the fluidity of the resin when melted. Olefin-based polymers or copolymers, such as isotactic polypropylene or propylene, with a small amount (less than 50% by weight, preferably 10-40% by weight) of other α-olefins, such as ethylene, 1-butene, 1 Examples include copolymers with -hexene, 4-methyl-1-pentene, and the like. Melt flow rate (MFR: ASTM-D-1238,
L conditions (230°C) are in the range of 0.1 to 50 g/10 minutes, preferably 1 to 30 g/10 minutes.

If the MFR is less than this range, the resulting molded product will have an unfavorable appearance due to flow marks, and if it exceeds this range, the low-temperature impact of the resulting molded product will deteriorate.

The blending ratio of this component is 60 to 70% by weight, preferably 63 to 70% by weight, based on the total amount of this component, component A described above, and component C described below. If it is less than this range, the appearance of the molded product and the mold releasability during molding will deteriorate, and if it exceeds this range, the low-temperature impact will be deteriorated.

Further, as the rubber softener of component C used in the present invention, non-aromatic mineral oil or a liquid or low molecular weight synthetic softener is suitable. As the non-aromatic softener, paraffinic and naphthenic softeners are preferred. Examples of synthetic softeners include polybutene and low molecular weight polybutadiene. The blending amount of this component is 5% to 25% by weight, preferably 7% to 25% by weight based on the total amount of this component and components A and B.
Weight%. If it is less than this range, the appearance of the molded product will deteriorate, and if it exceeds this range, low-temperature impact and mold release properties during molding will be deteriorated.

In addition, the specific components of components AXB and C and their blending ratios are based on the flexural modulus of 20, which is one of the constituent requirements of the present invention.
It is necessary to select a composition in the range of 00 to 4500 kg/c++l. 2000 for automobile exterior products
If it is less than 4,500 kg/cn, it will be too soft and there will be problems with installation, and if it exceeds 4,500 kg/cn, performance such as shock absorption and deformation recovery will deteriorate.

In such a composition according to the present invention, the above-mentioned essential component A
, B and C, pigments, stabilizers, antioxidants,
Additives such as ultraviolet absorbers can be added. Furthermore, inorganic fillers such as calcium carbonate, carbon black, talc, and clay can also be added.

Melt kneading is generally used as a method for dynamically heat-treating materials in the presence of peroxide, which is carried out in the present invention.

The kneading method may be a method commonly used for rubber, plastics, etc., and for example, a -screw extruder, a twin-screw extruder, a roll, a Banbury mixer, or various kneaders are used.

In addition, in the case where an extruder is used for dynamic heat treatment kneading in the presence of an organic peroxide, and if components A and C are difficult to extrude due to their shape (veil or liquid), It is effective to pre-blend all or a portion of components A, B and C using a roll, Banbury mixer, kneader or the like to form pellets.

The organic peroxide used in the present invention may be either aromatic or aliphatic, and may be a single peroxide or a mixture of two or more peroxides. Specifically, 2,5-dimethyl-2,5-di(benzoylperoxy)-hexane, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-
2,5-di(1-butylperoxy)-hexane, L-
Butylcumyl peroxide, diisopropylhenzohydroperoxide, 1,3-bis-(t-butylperoxyisopropyl)-benzene, hendyl peroxide, and the like are used.

゛In addition, as the crosslinking aid used in combination with the above peroxide, in addition to acrylic polyfunctional monomers such as ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane triacrylate, etc., divinylbenzene, liquid polybutadiene, etc. be.

In addition, examples of antioxidants that may be used include (1) monophenol compounds, and (2) bis.

Tris or polyphenol compounds, (3) thiobisphenol compounds, and (4) phenol compounds consisting of polyhydric phenols or derivatives thereof, (5) naphthylamine compounds, (6) diphenylamine compounds, or (7) p-phenylene. There are amine compounds made of diamine compounds.

+11 Compounds belonging to the heptanophenolic compound include 2
．． Examples include 6-di-butyl-p-cresol, 2,6-di-t-butylphenol, 2,4-dimethyl-6-L-butylphenol, and 2.4.6-)-t-butylphenol.

(2) Bis, tris or polyphenol compounds include 4,4-dihydroxydiphenyl, 2,2'-methylenebis(4-ethyl-6-t-butylphenol),
Tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, tetrakis[methylene-3-(3'
, 5'-di-t-butyl-4'-hydroxyphenyl)
Examples include comethane propionate.

(3) Thiobisphenol compounds include 4,4'-thiobis(6-1-butyl-3-methylphenol), 2
．． Examples include 2'-thiobis (6-butyl-4-methylphenol).

(4) Polyhydric phenols or derivatives thereof include monobutylhydro; thonone, and the like.

(5) Naphthylamine compounds include phenyl-α-naphthylamine.

(6) Diphenylamine compounds include p-isopropoxydiphenylamine.

(7) p-phenylenediamine compounds include N, N'
-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and the like.

Among them, the phenolic antioxidants (1), (2), and (3) are preferred.

The amounts of organic peroxide, crosslinking coagent and antioxidant used are 0.05 to 2.0 parts by weight of organic peroxide (preferably 1 part by weight) per 100 parts by weight of the formulation consisting of components A, B and C. is 0.08 to 1.0 parts by weight) Crosslinking aid 5
．． 0 parts by weight or less (preferably 0.1 to 2.0 parts by weight) Antioxidant 3 parts by weight or less (preferably 1 part by weight or less) However, in reality, the blending ratio of each essential component, especially the resulting molding It is determined by considering the degree of crosslinking, which affects the quality of the product.

The degree of crosslinking [wt%] of the molded product made of the partially crosslinked composition obtained according to the present invention is determined by wrapping 1 g of the sample in an 80 mesh wire mesh and extracting it with boiling xylene for 10 hours using a Soxhlet extractor. 1g sample of residual solid content weight
Expressed as a percentage of

In the present invention, the preferred degree of crosslinking is in the range of 1 to 25% by weight, preferably 5 to 20% by weight, based on the above measured values. The lower limit of this range is desired from the viewpoint of low-temperature impact and heat resistance, and the upper limit is desired from the viewpoint of the appearance of the molded product.

Molding methods for obtaining vehicle exterior parts using the obtained partially crosslinked composition include injection molding, extrusion molding, blow molding, and molding using commonly used thermoplastic resin molding machines. Components to which thermoplastic resin molding methods such as calendar molding can be applied (pigments, stabilizers, ultraviolet absorbers, etc.) can also be added.

Specific vehicle exterior parts include bumpers, fascias, fenders, air dams, air spoilers, moldings, front grilles, mantle guards, and the like.

〔Effect of the invention〕

According to the method of the present invention, it is possible to manufacture vehicle exterior parts with excellent quality such as low-temperature impact, heat resistance, and molded product appearance, and with a good overall quality balance by speeding up the molding cycle.

〔Example〕

The following examples and comparative examples specifically illustrate the present invention. The test methods used for various evaluations in these Examples and Comparative Examples are as follows.

+1) Gel fraction (weight %) After wrapping 1 g of the sample in an 80-mesh wire mesh and extracting it with boiling xylene using a Soxhlet extractor for about 10 hours, it is expressed as the ratio of the weight of the residual solid content to 1 g of the sample.

(2) Flexural modulus (kg/cffl) Compliant with JIS-7203.

(3) Appearance of the molded product The injection molded product (bumper weighing 3.5 kg) shown in Figure 1 was molded under the molding conditions shown in Table 1, and the presence or absence of flow marks and uneven gloss was visually evaluated ( Yes: ×, No; ○)
.

Furthermore, we visually checked for the presence or absence of crater-shaped or cloud-shaped sink marks on the surface of the molded product, and for crater-shaped sink marks, we cut the part vertically and observed the cross section to evaluate the presence or absence of air bubbles (sink marks and air bubbles were present). :×, none 20).

Table 1 (4) Molding properties Regarding the same injection molded products as in item (3) above, those with no problem in mold release are 0, and those that are molded from the cavity side or from the core side when opening and releasing the mold are 0. If it could not be ejected smoothly with an ejector pin, it was judged as ×.

Moreover, the shorter the plasticization time, the better.

In particular, the plasticization time that exceeds the cooling time will affect the molding cycle by that amount.

For large molded products such as bumpers, the cooling time is 30~
Since the plasticizing time is generally 35 seconds, a plasticizing time longer than this poses a problem in terms of productivity, and in this example, the plasticizing time was approximately 35 seconds.
．． When the plasticization time was 30 to 35 seconds for a 5 kg molded product, the evaluation was ◯, and when the plasticization time exceeded 40 seconds, it was evaluated as ×.

(5) The practical quality molded product (bumper) was fitted with a polypropylene foam (15 times foamed shock absorber) inside and attached to a predetermined jig at five points above and below in accordance with actual use.

The installed molded product was fixed horizontally, just like the actual bumper, and the smoothness (undulations) of the top surface of the molded product was checked. Those with large undulations when visually observed were rated ×, and those with hardly noticeable undulations were rated ○.

Regarding low-temperature impact strength, based on the United States Motor Vehicle Safety Standards (FMVSS), part 581,
An impact test was conducted at , and those with cracking were rated ×, and those with no cracking were rated ○. The shape of the molded product was evaluated 30 minutes after the impact test, and the amount of deformation of the molded product as a whole compared to the original shape was 3.
If the deformation was 74 inches or less and locally 3/8 inch or less, it was rated as ○, and if there was deformation exceeding that amount, it was rated as ×.

In addition, each component used in Examples and Comparative Examples is as follows.

a) Component A ・EP~1: Mooney viscosity ML, 11 (120°C) 2
20, iodine value 19, propylene content 28% by weight EP
DM ・EP-2: Mooney viscosity ML, 4 (100°C) 70
, IEPD with an iodine number of 15 and a propylene content of 27% by weight.
? j b) Component B ・PP-1: Propylene copolymer manufactured by Mitsubishi Yuka Co., Ltd. rB
c3EJ (MF R<230℃>10g/10min,
Ethylene content: 9% by weight) PP-2: Propylene copolymer rB manufactured by Mitsubishi Yuka Co., Ltd.
c03B J (VF R<230℃>33g/1
0 minutes, ethylene content 9% by weight) ・PP-37 Mitsubishi Yuka Co., Ltd. propylene copolymer rB
c5DJ (MFR<230℃>, 4g/10min,
(Ethylene content: 12% by weight) C) Component C: Paraffin oil PW90 manufactured by Idemitsu Kosan Co., Ltd.
J d) Organic peroxide: “Kayahexa ADJ <2.5-dimethyl-2,5-di(t-butylperoxy)-hexane> manufactured by Kayaku Nouri Co., Ltd. e) Crosslinking aid Nidivinylbenzene f) Antioxidant : Manufactured by Ciba Geigy [Irganox 10IOJ (
Polyphenol Derivatives) Two methods were used to produce the partially crosslinked compositions as described below.

<Method A> Among the ingredients, the entire amount of components A and C and a portion or the entire amount of component B are kneaded in a Banbury mixer at 170"C for 6 minutes), and then sheet canted to obtain pellets. Optionally, add the remaining component B using a two-screw extrusion machine, mix organic peroxide, crosslinking aid, and stabilizer, and dynamically crosslink at 200°C to partially crosslink. A composition was obtained.

Method B> Mix the total amount of components A and C of each component and a portion of component B (usually around 30% of the total component B) in a Banbury mixer at 170 ° C. for 6 minutes),
Thereafter, pellets are obtained by sheet cutting. Next, the obtained pellets were mixed with an organic peroxide, a crosslinking aid, and a stabilizer, and dynamically crosslinked at 200°C in a 45-tuna diameter twin-screw extruder to obtain a partially crosslinked composition. remaining ingredient B
were mixed and kneaded at 200° C. in a 40 mm diameter single screw extruder to obtain a partially crosslinked composition.

Note that method A is a method according to the present invention, and method B is a conventional method.

Examples and comparative examples The formulation, manufacturing method and quality of the composition are shown in Table 2.

Examples 1 to 5 all had appropriate flexibility, and had a good balance in appearance, moldability, and practical quality.

(Margin below)

[Brief explanation of the drawing]

FIG. 1 is a drawing of an automobile bumper. A indicates the injection gate section. FIG. 2 is a sectional view taken along the broken line in FIG. 1. Here, ゛, a is l 600 dragon, b is 300 am, C
is 700 layer theory 5d is 45 peng.

Claims (1)

[Claims] 1. A partially crosslinked thermoplastic resin composition is obtained by dynamically heat-treating a mixture of rubber, resin, and rubber softener in the presence of an organic peroxide. Then, in the method of molding this by a conventional method to form an automobile exterior part, each of the following components A to C is used as a compounding component of the mixture, and the JIS-K of the thermoplastic resin composition is used.
-7203 bending elastic modulus is 2000 to 4500 kg
/cm^2 range. Component A: Mooney viscosity is ML_1_+_4 (100℃)
10 to ML_1_+_8 (120°C) 300, 10 to 35% by weight of peroxide crosslinked rubber with iodination of 30 or less and propylene content of 25 to 50% by weight Component B: peroxide with a melt flow rate of 0.1 to 50 g/10 min Degradable olefin resin 60-70% by weight Component C: Rubber softener 5-25% by weight