JP4241327B2 - Resin composition for airbag cover - Google Patents

Description

  The present invention relates to a resin composition that provides an airbag cover that has excellent appearance and good low-temperature strength.

  The airbag cover of an automobile airbag system is required to burst reliably so that the airbag can be deployed in the event of a collision, and the fragments should not scatter and have low-temperature strength to withstand use in cold regions. . Nowadays, it is further required that it can be used without being coated, that is, a good texture pattern is applied. Examples of the material used for the airbag cover include a resin composition containing a polypropylene resin, an ethylene / butene copolymer rubber and an ethylene / propylene copolymer rubber, and a polypropylene resin and an ethylene-propylene-nonconjugated diene. A resin composition containing a copolymer rubber and a low crystalline propylene-1-butene copolymer has been proposed (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

JP-A-10-273001 JP-A-10-279745 JP 2000-72937 A

However, in the airbag cover using the above resin composition, gloss unevenness occurs due to the unevenness of the wrinkle pattern in the vicinity of the so-called burst line or tear line where the cover is torn when the airbag is deployed. The appearance was not satisfactory enough.
Under such circumstances, the problem to be solved by the present invention is to provide a resin composition from which an airbag cover having excellent appearance and good low-temperature strength can be obtained, and an airbag cover comprising the resin composition. .

That is, the first of the present invention contains the following components (A) and (B), the total of component (A) and component (B) is 100% by weight, and the content of component (A) is 40-60. It is a resin composition for paintless airbag covers in which the content of component (B) is 60 to 40 % by weight.
(A): a monomer unit based on ethylene, a monomer unit based on propylene, and a monomer unit based on at least one α-olefin selected from 1-butene, 1-hexene and 1-octene And an ethylene polymer satisfying the following requirements (1) and (2) Requirement (1): The following formula (A) must be satisfied.
x> y + z (I)
(X represents the content (mol%) of monomer units based on ethylene in the ethylene polymer, and y represents the content (mol%) of monomer units based on propylene in the ethylene polymer. , Z represents the content (mol%) of monomer units based on α-olefin of 1-butene, 1-hexene, 1-octene in the ethylene polymer, provided that the total amount of x, y and z is 100 mol%)
Requirement (2): The peak temperature of the melting peak measured by a differential scanning calorimeter (DSC) is 100 ° C. or lower, or no melting peak is observed.
(B): Propylene-based resin The second aspect of the present invention is a coating-less airbag cover made of the resin composition.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a resin composition from which an airbag cover having excellent appearance and good low-temperature strength can be obtained, and an airbag cover comprising the resin composition.

Component (A) includes a monomer unit based on ethylene, a monomer unit based on propylene, and a monomer based on at least one α-olefin selected from 1-butene, 1-hexene and 1-octene. 1 -butene is more preferable as the α -olefin.

  Examples of the component (A) include an ethylene-propylene-1-butene copolymer, an ethylene-propylene-1-hexene copolymer, and an ethylene-propylene-1-octene copolymer. -Propylene-1-butene copolymer.

The ethylene polymer of component (A) is a polymer that satisfies the following formula (A).
x> y + z (I)
Here, x represents the content (mol%) of monomer units based on ethylene in the ethylene polymer, and y represents the content (mol%) of monomer units based on propylene in the ethylene polymer. Z represents the content (mol%) of monomer units based on α-olefin of 1-butene, 1-hexene and 1-octene in the ethylene-based polymer. However, the total amount of x, y and z is 100 mol%. If the above formula (A) is not satisfied, the low temperature strength may be inferior. In addition, content of each monomer unit is calculated | required by NMR analysis.

  The ethylene-based polymer of component (A) is a polymer having a peak temperature of a melting peak measured by a differential scanning calorimeter (DSC) of 100 ° C. or lower, or a melting peak not observed. The ethylene polymer as the component (A) is preferably a polymer having a melting peak peak temperature of 80 ° C. or lower, or a melting peak not observed. In addition, melting peak temperature is calculated | required by measuring on the conditions that a temperature increase rate and temperature decrease rate are 10 degree-C / min according to JISK7121.

  The melt flow rate of the ethylene-based polymer of component (A) is preferably 15 g / 10 min or less, more preferably 7 g / 10 min or less, from the viewpoint of increasing mechanical strength. Moreover, from a viewpoint of improving injection moldability, Preferably it is 0.1 g / 10min or more, More preferably, it is 0.5 g / 10min or more. The melt flow rate is measured according to JIS K7210 under conditions of a load of 98.06 N and a temperature of 190 ° C.

Component (A) ethylene polymer can be produced using a known Ziegler-Natta type catalyst or a known single-site catalyst (metallocene, etc.). From the standpoint of further improving the above, a known single site catalyst (metallocene, etc.) is preferable. Examples of such a single site catalyst include, for example, JP-A-58-19309, JP-A-60-35005, JP-A-60-35006, JP-A-60-35007, JP-A-60-35008, JP-A-61-130314, JP-A-3-163088, JP-A-4-268307, As described in JP-A-9-12790, JP-A-9-87313, JP-A-11-80233, JP10-508055, etc. Talocene catalyst: JP-A-10-316710, JP-A-11-1000039, JP-A-11-80228, JP-A-11-80227, JP-T-10-513289, JP-A-10-338706 And non-metallocene complex catalysts described in JP-A-11-71420 and the like. Among these, metallocene catalysts are preferable from the viewpoint of availability, and among them, examples of suitable metallocene catalysts include at least one cyclopentadiene-type anion skeleton and a periodic table having a C ₁ enantiomeric structure. A transition metal complex of Group 12 to Group 12 is preferred. Further, as an example of a production method using a metallocene catalyst, the method of European Patent Application Publication No. 12111287 can be exemplified. It is also possible to use commercially available products.

  The propylene-based resin of component (B) is a polymer in which the content of monomer units based on propylene exceeds 50% by weight (provided that the content of all monomer units in the polymer is 100% by weight) And a melting point of 100 ° C. or higher. Here, the melting point is a peak temperature of a melting peak measured in accordance with JIS K7121 under conditions of a heating rate and a cooling rate of 5 ° C./min. When there are a plurality of melting peaks, the melting temperature is the maximum. The peak temperature of the peak is taken as the melting point.

Examples of the propylene resin include the following polymers (B1) to (B3).
Polymer (B1): Propylene homopolymer polymer (B2): Propylene-ethylene random copolymer polymer (B3): Propylene-ethylene block copolymer satisfying the following requirements (i) or (ii) (i): It consists of two segments, and one segment (hereinafter referred to as “segment (X)”) is a propylene homopolymer portion or a propylene-ethylene random copolymer portion, and the other segment (hereinafter referred to as “segment”). (Y) ") is a propylene-ethylene random copolymer part.
(Ii) The content of the monomer unit based on ethylene in the segment (Y) is larger than the content of the monomer unit based on ethylene in the segment (X).

  The content of the monomer units based on ethylene in the polymer (B2) is set so that the total monomer unit content in the polymer is 100% by weight from the viewpoint of improving the heat resistance of the resulting resin composition. It is preferable that it is 10 weight% or less.

From the viewpoint of enhancing the heat resistance of the resulting resin composition, the polymer (B3) preferably further satisfies the following requirement (iii), and further preferably satisfies the following requirement (iv). It is preferable to satisfy (v).
(Iii): The content of monomer units based on ethylene in the segment (X) is 10% by weight or less (however, the total monomer unit content in the segment (X) is 100% by weight) .)
(Iv): The content of monomer units based on ethylene in the segment (Y) is 50% by weight or less (however, the total monomer unit content in the segment (Y) is 100% by weight) .)
(V): The content of the segment (Y) is 70% by weight or less (however, the polymer (B3) is 100% by weight).

  From the viewpoint of facilitating molding, the melt flow rate of the propylene-based resin as the component (B) is preferably 0.1 g / 10 minutes or more, more preferably 1 g / 10 minutes or more. The melt flow rate is preferably 150 g / 10 min or less, more preferably 100 g / 10 min or less, from the viewpoint of increasing mechanical strength. The melt flow rate is measured according to JIS K7210 at a load of 21.18 N and a temperature of 230 ° C.

  As a method for producing the component (B) propylene-based resin, a known polymerization method using a known olefin polymerization catalyst is used. Examples thereof include a thriller polymerization method, a solution polymerization method, a bulk polymerization method, and a gas phase polymerization method using a complex catalyst such as a Ziegler-Natta catalyst, a metallocene complex, or a nonmetallocene complex. It is also possible to use commercially available products.

  In the resin composition of the present invention, the content of the component (A) and the component (B) is 100% by weight of the sum of the component (A) and the component (B), and the content of the component (A) is 30 to 30%. 90% by weight, the content of component (B) is 70 to 10% by weight, preferably the content of component (A) is 30 to 70% by weight, and the content of component (B) is 70%. The content of the component (A) is 40 to 60% by weight, and the content of the component (B) is 60 to 40% by weight. If the content of the component (A) is too small (the content of the component (B) is too large), a good appearance may not be obtained or the low-temperature impact performance may be deteriorated, and the content of the component (A) When there is too much (content of a component (B) is too little), heat resistance may fall, or a moldability may fall.

  The flexural modulus of the resin composition of the present invention is preferably 100 to 800 MPa. More preferably, the pressure is 100 to 300 MPa from the viewpoint of use for the driver airbag cover, and more preferably 200 to 800 MPa from the viewpoint of use for the passenger airbag cover, side airbag cover, and knee airbag cover. It is. The flexural modulus is measured according to JIS K7203.

  The resin composition according to the present invention includes, as necessary, inorganic fillers such as talc, calcium carbonate, and calcined kaolin; organic fillers such as fiber, wood powder, and cellulose powder; lubricants such as fatty acid amide, silicone oil, and silicone gum; Antioxidants such as sulfur, phosphorus, lactone and vitamins; weathering stabilizers; UV absorbers such as benzotriazoles, triazines, anilides and benzophenones; heat stabilizers; hindered amines and benzoates Light stabilizers; pigments; nucleating agents; metal oxides (eg zinc oxide, magnesium oxide), metal chlorides (eg iron chloride, calcium chloride), hydrotalcite and aluminate adsorbents May be.

  There is no restriction | limiting in particular as the adjustment method of the resin composition of this invention, A component (A) and a component (B) are required, using a well-known method, for example, a tumbler blender, a Henschel mixer, a Banbury mixer, an extruder, etc. Depending on the method, there may be mentioned a method of melt mixing with other components.

  The resin composition of the present invention is molded into an airbag cover by a known molding method, for example, an injection molding method. The airbag cover is suitably used for a driver seat airbag cover, a passenger seat airbag cover, a side airbag cover, and a knee airbag cover. In particular, it is suitably used for an airbag cover that is used without painting, such as a paintless driver's seat airbag cover and a paintless passenger seat airbag cover.

Hereinafter, the present invention will be described in more detail by way of examples.
[I] Physical property measuring method (1) Content of each monomer unit of copolymer ¹ H-NMR spectrum, ¹³ C-NMR spectrum using nuclear magnetic resonance apparatus (trade name AC-250 manufactured by Bruker) It calculated based on the measurement result. Specifically, in the ¹³ C-NMR spectrum, from the ratio of the spectral intensity of methyl carbon derived from the propylene monomer unit to the spectral intensity of methyl carbon derived from the 1-butene monomer unit, the propylene monomer unit and 1 -The composition ratio of the butene monomer unit was calculated, and then in the ¹ H-NMR spectrum, the ethylene unit amount was determined from the ratio between the spectral intensity of hydrogen derived from the methine unit and the methylene unit and the spectral intensity of hydrogen derived from the methyl unit. The composition ratio of the body unit, the propylene monomer unit and the 1-butene monomer unit was calculated.
(2) Melt flow rate (MFR)
According to JIS K7210, the measurement was performed under conditions of a temperature of 230 ° C. and a load of 21.18 N.
(3) Melting peak temperature According to JIS K7121, it measured with the differential scanning calorimeter (Seiko Electronics Co., Ltd. DSC220C: input compensation DSC). Specifically, as a condition adjustment, the temperature was increased from room temperature to 200 ° C. at 30 ° C./min, held at 200 ° C. for 5 minutes, then cooled to −100 ° C. at 10 ° C./min, and at −100 ° C. for 5 minutes. Retained. Next, the temperature was raised from −100 ° C. to 200 ° C. at 10 ° C./min, and the melting peak was measured.

(4) Rigidity Flexural modulus was measured according to JIS K7203.
(5) Low temperature strength According to JIS K6911, the Izod impact test at -40 degreeC was done and evaluated as follows.
NB: Not destroyed.
B: Destroyed.
(6) Appearance evaluation Using a mold having a crimped mold (FIGS. 1 and 2) for molding a molded body whose thickness rapidly changes from 2 mm to 1 mm, injection molding is performed under the following conditions using an injection molding machine. The appearance of the portion where the thickness of the obtained molded body was changed was evaluated.
<Molding conditions>
Injection molding machine: IS100EN-3A manufactured by Toshiba Machine Co., Ltd.
Mold temperature: 50 ℃
Cylinder temperature: 220 ° C (nozzle part)
Injection pressure: 90%
Injection time: 10 seconds Injection speed: 4-stage switching
Screw position 95-55mm: 30%
Screw position 55-35mm: 60%
Screw position 35-10mm: 30%
Screw position 10-5mm: 10%
Holding pressure switching screw position: 5mm
Back pressure: 5%
Holding pressure: Yes (set value: 5, 10, 15 or 20%) or No (set value: 0%)
<Evaluation>
○: The gloss unevenness is not known under all conditions where pressure is applied.
Δ: Gloss unevenness can be seen under any condition where pressure is applied, but gloss is not known under conditions where pressure is not applied.
X: Uneven gloss can be clearly seen under conditions where no holding pressure is applied.

[II] Raw material (A) Ethylene-propylene-1-butene copolymer A-1: Ethylene-propylene-1-butene copolymer In a 100 L SUS polymerizer equipped with a stirrer, hydrogen was used for molecular weight adjustment. Then, ethylene, propylene and 1-butene were continuously copolymerized by the following method to obtain an ethylene-propylene-1-butene copolymer.
From the lower part of the polymerization vessel, hexane as a polymerization solvent at a feed rate of 239 L / hour, ethylene at a feed rate of 3.27 Kg / hour, propylene at a feed rate of 0.70 Kg / hour, and 1-butene at 6. Each was continuously supplied at a supply rate of 23 kg / hour.
The reaction mixture is continuously withdrawn from the upper part of the polymerization vessel so that the amount of the reaction mixture in the polymerization vessel is maintained at 100 L. From the lower part of the polymerization vessel, dimethylsilyl (tetramethylcyclopentadibenzene) is used as a component of the polymerization catalyst. Enyl) (3-tert-butyl-5-methyl-2-phenoxy) titanium dichloride at a feed rate of 0.017 g / hr and triphenylmethyltetrakis (pentafluorophenyl) borate at a feed rate of 0.967 g / hr. Triisobutylaluminum was continuously fed at a feed rate of 1.984 g / hr.
The copolymerization reaction was carried out at 42 ° C. by circulating cooling water through a jacket attached to the outside of the polymerization vessel.
A small amount of ethanol is added to the reaction mixture continuously withdrawn from the top of the polymerization vessel to stop the polymerization reaction, followed by demonomerization and water washing, and then the solvent is removed by steam in a large amount of water. Thus, an ethylene-propylene-1-butene copolymer was obtained, and this was dried under reduced pressure at 80 ° C. for 1 day. The production rate of the copolymer was 3.06 Kg / hour.
The resulting copolymer had an ethylene monomer unit content of 54 mol%, a propylene monomer unit content of 7 mol%, and a 1-butene monomer unit content of 39 mol%, and a differential scanning calorific value. The melting peak was not observed in the analysis by the meter.
(B) Propylene resin B-1: Sumitomo Mitsui Polyolefin Co., Ltd. Sumitomo Mitsui Polypro Z144A
(MFR = 25g / 10min)
B-2: Sumitomo Mitsui Polyolefin Co., Ltd. Sumitomo Mitsui Polypro AZ161C1
(MFR = 32g / 10min)
B-3: Sumitomo Mitsui Polyolefin Z101 manufactured by Sumitomo Mitsui Polyolefin
(MFR = 22g / 10min)
(C) Other C-1: Esplen 512P manufactured by Sumitomo Chemical Co., Ltd.
(Ethylene-propylene copolymer rubber ethylene monomer unit = 78 mol%, propylene monomer unit = 22 mol%)
C-2: Esplen 201 manufactured by Sumitomo Chemical Co., Ltd.
(Ethylene-propylene copolymer rubber ethylene monomer unit = 57 mol%, propylene monomer unit = 43 mol%)
C-3: Esplen SPO N0391 manufactured by Sumitomo Chemical Co., Ltd.
(Ethylene-1-butene copolymer rubber ethylene monomer unit = 91 mol%, 1-butene monomer unit = 9 mol%)
C-4: Propylene-1-butene copolymer In a 100 L SUS polymerizer equipped with a stirrer, propylene and 1-butene were continuously copolymerized by the following method using hydrogen as molecular weight control. A propylene-1-butene copolymer was obtained.
From the lower part of the polymerization vessel, hexane as a polymerization solvent was continuously fed at a feeding rate of 100 L / hour, propylene was fed at a feeding rate of 24.00 Kg / hour, and 1-butene was fed at a feeding rate of 1.81 Kg / hour. Supplied.
From the top of the polymerization vessel, the reaction mixture was continuously withdrawn so that the reaction mixture in the polymerization vessel maintained an amount of 100 L.
From the lower part of the polymerization vessel, as a component of the polymerization catalyst, dimethylsilyl (tetramethylcyclopentadienyl) (3-tert-butyl-5-methyl-2-phenoxy) titanium dichloride is supplied at a rate of 0.005 g / hour, Triphenylmethyltetrakis (pentafluorophenyl) borate was continuously fed at a feed rate of 0.298 g / hr and triisobutylaluminum was fed at a feed rate of 2.315 g / hr.
The copolymerization reaction was carried out at 45 ° C. by circulating cooling water through a jacket attached to the outside of the polymerization vessel.
By adding ethanol to the reaction mixture continuously withdrawn from the top of the polymerization vessel to stop the polymerization reaction, followed by demonomerization and water washing, and then removing the solvent with steam in a large amount of water, A propylene-1-butene copolymer was obtained and dried under reduced pressure at 80 ° C. for 1 day. The production rate of the copolymer was 7.10 kg / hour.
The resulting copolymer had a propylene monomer unit content of 96 mol% and a 1-butene monomer unit content of 4 mol%, and no melting peak was observed by analysis with a differential scanning calorimeter. .

Example 1
50% by weight of (A-1) and 50% by weight of (B-1) were melt-kneaded with a Banbury mixer and then granulated to obtain resin composition pellets. Using an injection molding machine, the pellets were molded into a flat plate having a thickness of 2 mm and 150 mm × 90 mm under conditions of a cylinder temperature of 220 ° C. and a mold temperature of 50 ° C. Table 1 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

Example 2
(B-1) The procedure was performed in the same manner as in Example 1 except that 50% by weight of (B-2) was used instead of 50% by weight. Table 1 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

Example 3
The same operation as in Example 2 was performed except that (A-1) was 40% by weight and (B-2) was 60% by weight. Table 1 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

Example 4
(B-1) The procedure was the same as Example 1 except that 50 wt% of (B-3) was used instead of 50 wt%. Table 1 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

Example 5
The same operation as in Example 4 was performed except that (A-1) was 40% by weight and (B-3) was 60% by weight. Table 1 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

Comparative Example 1
(B-1) 50% by weight, (C-1) 40% by weight, and (C-2) 10% by weight were melt-kneaded with a Banbury mixer, and then granulated into pellets. Using an injection molding machine, the pellets were molded into a flat plate having a thickness of 2 mm and 150 mm × 90 mm under conditions of a cylinder temperature of 220 ° C. and a mold temperature of 50 ° C. Table 2 shows the evaluation results of the obtained flat plate.

Comparative Example 2
(C-1) It replaced with 40 weight% and (C-2) 10 weight%, and performed similarly to the comparative example 1 except having used 50 weight% of (C-3). Table 2 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

Comparative Example 3
50% by weight of (B-1) and 50% by weight of (C-4) were melt-kneaded with a Banbury mixer, and then granulated into pellets. Using an injection molding machine, the pellets were molded into a flat plate having a thickness of 2 mm and 150 mm × 90 mm under conditions of a cylinder temperature of 220 ° C. and a mold temperature of 50 ° C. Table 2 shows the evaluation results of the obtained flat plate.

Comparative Example 4
(B-1) The procedure was the same as Comparative Example 3 except that 50% by weight of (B-2) was used instead of 50% by weight. Table 2 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

Comparative Example 5
(B-1) The same procedure as in Comparative Example 3 was conducted except that 50% by weight of (B-3) was used instead of 50% by weight. Table 2 shows the evaluation results of the obtained resin composition pellets and injection molded articles.

It is a schematic diagram of the cross section of the type | mold with a grain used for shaping | molding of the molded object for external appearance evaluation. It is a schematic diagram of the inner front of the embossed die used for molding the molded article for appearance evaluation.

Claims (3)

The following components (A) and (B) are contained, the total of component (A) and component (B) is 100% by weight, the content of component (A) is 40 to 60 % by weight, and component (B) The resin composition for coating-less airbag covers whose content is 60 to 40 % by weight.
(A): a monomer unit based on ethylene, a monomer unit based on propylene, and a monomer unit based on at least one α-olefin selected from 1-butene, 1-hexene and 1-octene And an ethylene polymer satisfying the following requirements (1) and (2) Requirement (1): The following formula (A) must be satisfied.
x> y + z (I)
(X represents the content (mol%) of monomer units based on ethylene in the ethylene polymer, and y represents the content (mol%) of monomer units based on propylene in the ethylene polymer. , Z represents the content (mol%) of monomer units based on 1-butene, 1-hexene and 1-octene in the ethylene polymer, provided that the total amount of x, y and z is 100 mol%. To do.)
Requirement (2): The peak temperature of the melting peak measured by a differential scanning calorimeter (DSC) is 100 ° C. or lower, or no melting peak is observed.
(B): Propylene resin A resin composition for an airbag cover, wherein the component (A) according to claim 1 is an ethylene polymer that satisfies the requirement (1) and the following requirement (3).
Requirement (3): No melting peak is observed by a differential scanning calorimeter (DSC).   A resin composition for an airbag cover, wherein the component (A) according to claim 1 or 2 is an ethylene polymer produced using a single site catalyst.

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