JP2004211066A - Shock-absorbing material and shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock-absorbing material which is produced by a bead molding method (an in-mold molding method) under a low steam pressure and exhibits good shock-absorbing characteristics and strain recovery; and to provide a shock absorber using the same. <P>SOLUTION: The shock-absorbing material 1 is obtained by placing foamed particles in a mold to effect molding. (a) The base resin of the foamed particles is a propylene polymer comprising 100-85 mol% propylene-derived structural units and 0-15 mol% structural units derived from ethylene and/or a 4-20C α-olefin. (b) In the propylene polymer, the proportion of position irregular units (measured by 13C-NMR) based on the 2,1-insertion of propylene monomer units in the entire propylene insertion is 0.5-2.0%; and the proportion of position irregular units based on the 1,3-insertion is 0.005-0.4%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a shock absorber that can be used as a core material of an automobile bumper, and a shock absorber having the shock absorber.

  At present, as a vehicle bumper, a synthetic material arranged to fill part, most or all of the space between the reinforcement and the synthetic resin skin material, and furthermore, the space between the reinforcement and the synthetic resin skin material. What consists of a core material made of resin foam is widely used. By using a synthetic resin foam as the core material in this way, an automobile bumper has excellent shock absorption.

  In general, shock absorbers such as core materials for automobile bumpers include (1) excellent energy absorption performance, (2) excellent dimensional recovery, and (3) low density and light weight. Are required to be satisfied at the same time.

  In order to achieve this object, a technique using polypropylene (see Patent Document 1), a technique using an ethylene-propylene copolymer (see Patent Document 2), a 1-butene-propylene A technique using a polymer (see Patent Document 3) has been proposed.

  When manufacturing shock-absorbing materials, such as core materials for automobile bumpers, using polypropylene resin as the base resin, generally, foamed particles containing polypropylene resin as the base resin are filled in a mold and heated to form the expanded particles. A so-called bead molding method is used in which a foam is expanded and the particles are fused with each other to obtain a molded article according to a mold. The molded article of expanded polypropylene resin particles obtained by this method has characteristics such as excellent cushioning and resilience, light weight and small residual strain.

  Therefore, the shock absorbing material made of the foamed molded article of the polypropylene-based resin particles has excellent properties as compared with the shock absorbing material made of another material resin. However, on the other hand, rigidity and energy absorption efficiency were not always satisfactory.

In order to solve the above problem, a technique has been proposed in which a specific propylene homopolymer is further used as a base resin of an impact absorbing material such as a core material of a bumper (see Patent Document 4).
The expanded particles further containing the specific propylene homopolymer as a base resin are characterized in that the energy absorption efficiency of the shock absorber obtained by bead molding (in-mold molding) is superior to that of the conventional product.

However, the technique using the above-mentioned specific propylene homopolymer requires a high pressure of 5.0 to 6.0 kg / cm ² (gauge pressure) as a vapor pressure required for bead formation. Therefore, there is a problem that the cost required for molding the shock absorbing material is increased and the molding cycle is lengthened. Another problem is that the higher the energy absorption efficiency, the poorer the recovery of strain after impact.

Patent Document 5 proposes expanded polypropylene resin particles using an isotactic polypropylene resin polymerized using a metallocene polymerization catalyst as a base resin.
In this case, the vapor pressure required for bead molding can be relatively low, but the molded article obtained by using such expanded particles has a problem that the compression set is large, and further improvement has been desired. .

JP-A-58-221745 (Claims) JP-A-60-189660 (Claims) JP-A-2-158441 (Claims) International Publication WO98 / 06777 Pamphlet (Claims) JP-A-6-240041 (Claim 1)

  The present invention has been made in view of such conventional problems, and can be manufactured by a bead molding method (in-mold molding method) using a low water vapor pressure, and has good shock absorption characteristics and strain recovery. It is an object of the present invention to provide a shock absorber and a shock absorber as shown.

A first invention is a shock absorbing material formed by placing foamed particles in a molding die,
An impact-absorbing material, wherein the foamed particles contain a propylene-based polymer having the following requirements (a) and (b) as a base resin.
(A) 100 to 85 mol% of structural units obtained from propylene, and 0 to 15 mol% of structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms (provided that propylene is obtained from propylene) The total amount of the structural units and the structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms is 100 mol%).
(B) The ratio of the position irregular units based on the 2,1-insertion of the propylene monomer unit in the total propylene insertion is 0.5 to 2.0%, and the ratio of the propylene monomer unit is 1%, as measured by 13C-NMR. , 3- The ratio of the position irregular units based on insertion is 0.005 to 0.4%.

The impact absorbing material of the first invention is formed by molding foamed particles using a specific propylene polymer having the above requirements (a) and (b) as a base resin.
Therefore, the impact absorbing material has excellent energy absorption efficiency at impact, rigidity, and strain recovery by utilizing the excellent characteristics (high rigidity and high tenacity) of the specific propylene-based polymer.

  Further, the shock absorbing material of the present invention has excellent energy absorption efficiency as described above. Therefore, at the time of molding, the impact absorbing material can be made lighter by increasing the expansion ratio, or the thickness of the impact absorbing material can be reduced. The shock absorbing material can maintain a sufficient energy absorption efficiency even if the weight is reduced as described above.

  Further, the impact absorbing material is formed by placing foamed particles containing a specific propylene-based polymer as a base resin as described above in a mold. For this reason, the pressure of the necessary steam can be reduced when the expanded particles are formed by, for example, a bead forming method. Further, the time required for cooling during molding can be shortened. That is, the amount of energy required for molding the shock absorbing material can be reduced.

  As described above, according to the present invention, it is possible to provide a shock absorbing material which can be manufactured by a bead forming method (in-mold forming method) using a low water vapor pressure, and has good shock absorbing characteristics and strain recovery. be able to.

  A second invention is a shock absorber characterized in that a skin material is provided on the surface of the shock absorber of the first invention (claim 9).

The shock absorber of the second invention is provided with a skin material on the surface of the shock absorber of the first invention (claim 1), for example, so as to cover the shock absorber.
Therefore, in the shock absorber, the shock absorber absorbs the energy at the time of the shock as described above, and the skin material provided on the surface of the shock absorber improves the strength of the shock absorber. Can be.
Other effects are the same as those of the first invention.

In the present invention, the expanded particles use a propylene-based polymer having the above requirements (a) and (b) as a base resin.
Here, the base resin means a basic resin component constituting the expanded particles. The foamed particles may contain the base resin and other polymer components to be added as necessary, or additives such as a foaming agent, a catalyst neutralizing agent, a lubricant, a crystal nucleating agent, and other additives. Good. However, it is desirable that other polymer components and additives be as small as possible within a range not to impair the object of the present invention.
That is, when the propylene-based polymer is 100 parts by weight, the amount of the other polymer component added is preferably 40 parts by weight or less. More preferably, the amount is 30 parts by weight or less, and even more preferably 15 parts by weight or less. Most preferably, the amount is 5 parts by weight or less.
Further, when the propylene-based polymer is 100 parts by weight, the amount of the additive (excluding a foaming agent which does not eventually disperse, such as a foaming agent) depends on the purpose of use of the additive. It is preferably at most part by weight. More preferably, the amount is 30 parts by weight or less, and still more preferably 0.001 to 15 parts by weight.

First, the requirement (a) will be described.
The requirement (a) is that 100 to 85 mol% of a structural unit obtained from propylene and 0 to 15 mol% of a structural unit obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms are present.
Here, the total amount of the structural units obtained from propylene and the structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms is 100 mol%.
Therefore, the propylene-based polymer satisfying the requirement (a) includes a propylene homopolymer or a copolymer of propylene with ethylene and / or an α-olefin having 4 to 20 carbon atoms.

  Specific examples of the comonomer ethylene and / or an α-olefin having 4 to 20 carbon atoms copolymerized with propylene include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4- Methyl-1-pentene and the like can be mentioned.

  In the present invention, as the propylene polymer satisfying the above requirement (a), a polymer obtained by copolymerizing propylene with another monomer which has been difficult to polymerize with a conventional Ziegler / Natta catalyst can be used. In this case, the content of the structural unit obtained from the other monomer is preferably 0.01 to 20 mol%, more preferably 0.05 to 10 mol%, in the propylene polymer.

  Such other monomers include, for example, cycloolefins such as cyclopentene, norbornene, 1,4,5,8-dimethano-1,2,3,4,4a, 8,8a, 5-octahydronaphthalene, Chain non-conjugated dienes such as methyl-1,4-hexadiene, 7-methyl-1,6-octadiene, 4-ethylidene-8-methyl-1,7-nonadiene, 5-ethylidene-2-norbornene, dicyclopentadiene Or one or more selected from cyclic non-conjugated polyenes such as 1,5-vinyl-2-norbornene and norbornadiene, and aromatic unsaturated compounds such as styrene and divinylbenzene.

  As described in the requirement (a), the propylene polymer used in the present invention is a propylene (co) polymer resin containing 85 mol% to 100 mol% of a structural unit obtained from propylene in the propylene polymer. It is necessary that a structural unit obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms be contained in a proportion of 0 to 15 mol%.

  If the structural unit of propylene and the structural unit of ethylene and / or α-olefin as a comonomer are out of the above range (more than 15 mol%), mechanical properties such as bending strength and tensile strength of the base resin are used. Therefore, the rigidity and energy absorption efficiency of the shock absorbing material cannot be improved.

  In the propylene-based polymer, 98 to 85 mol% of structural units obtained from propylene and 2 to 15 mol% of structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms are present. (However, the total amount of the structural units obtained from propylene and the structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms is 100 mol%).

  In this case, the structural units obtained from propylene and the structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms are essential components. The expanded particles containing such a propylene-based polymer as the base resin have excellent secondary expandability when molded in a mold.

In the propylene-based polymer, the structural unit obtained from propylene can be 100 mol%, that is, the structural unit obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms can be 0 mol%.
In this case, the propylene-based polymer is a so-called propylene homopolymer. The impact absorbing material obtained by using such a propylene-based polymer is more excellent in strength.

  Next, as shown in the requirement (b), the propylene-based polymer has a ratio of the position irregular units based on the 2,1-insertion of the propylene monomer unit in the total propylene insertion measured by 13 C-NMR of 0. 0.5 to 2.0%, and the proportion of the position irregular units based on the 1,3-insertion of the propylene monomer unit is 0.005 to 0.4%.

  By using a propylene-based polymer containing each of these two types of positional irregular units in the above amounts as the base resin, the rigidity is increased and the toughness is increased. The impact absorbing material formed by molding foamed particles made of the base resin has an effect that rigidity, energy absorption efficiency, and strain recovery are remarkably high.

  When the ratio of the position irregular units based on the 2,1-insertion is less than 0.5%, or when the ratio of the position irregular units based on the 1,3-insertion is less than 0.005%, There is a problem that the strain recovery of the shock absorbing material obtained by molding the expanded particles is reduced.

  On the other hand, when the ratio of the position irregular units based on the 2,1-insertion exceeds 2.0%, or when the ratio of the position irregular units based on the 1,3-insertion exceeds 0.4%, In addition, there is a problem that mechanical properties such as bending strength and tensile strength of the propylene-based polymer are reduced. As a result, there is a problem that rigidity and energy absorption efficiency of the expanded particles containing the propylene-based polymer as a base resin and the impact absorbing material formed by molding the expanded particles are reduced.

  In the above requirement (b), the positional irregularity unit based on the 2,1-insertion and the positional irregularity unit based on the 1,3-insertion are both crystals of the propylene-based polymer containing these units in the structure. Has the effect of reducing the properties. More specifically, these regio-irregular units have an action of lowering the melting point and an action of lowering the crystallinity of the polypropylene-based polymer.

  These two effects show the effect of increasing the foaming suitability when such a base resin is subjected to foaming, and the effect of reducing the compression set of the obtained shock absorbing material.

  However, if the proportion of the position irregular units contained in the polypropylene-based resin is too high, the melting point and the crystallinity of the propylene-based polymer are highly reduced, so that the propylene-based polymer is used. When subjected to foaming, there is a possibility that a problem that the cell diameter in the obtained foamed particles becomes large may occur, in which case, the appearance of the shock absorbing material obtained from the foamed particles is impaired. Problem. Further, as described above, there is a problem that the strength of the shock absorbing material obtained from the expanded particles is reduced.

Here, the structural unit obtained from propylene in the propylene-based polymer, the fraction of ethylene and / or the structural unit obtained from an α-olefin having 4 to 20 carbon atoms, and the isotactic triad fraction described below are: , 13C-NMR method.
The method of measuring the 13C-NMR spectrum is, for example, as follows.
That is, about 350 to 500 mg of a sample was placed in a sample tube for NMR having a diameter of 10 mmφ, and completely dissolved using about 2.0 ml of o-dichlorobenzene as a solvent and about 0.5 ml of deuterated benzene for rock. Thereafter, the measurement was performed at 130 ° C. under the condition of complete proton decoupling.

As the measurement conditions, a flip angle of 65 deg and a pulse interval of 5T1 or more (where T1 is the longest value among the spin lattice relaxation times of the methyl group) were selected. In the propylene polymer, since the spin lattice relaxation time of the methylene group and the methine group is shorter than that of the methyl group, the recovery of the magnetization of all carbons is 99% or more under this measurement condition.
In addition, the detection sensitivity of the position irregular unit in the 13C-NMR method is usually about 0.01%, but it can be increased by increasing the number of integrations.

  The chemical shift in the above measurement was determined by setting the peak of the methyl group in the third unit of the five propylene units having 5 head-to-tail bonds and the same direction of methyl branching as 21.8 ppm. The chemical shifts of other carbon peaks were set.

  Using this criterion, the peak based on the methyl group of the second unit in the 3 chains of propylene units represented by PPP [mm] in the following formula [Chemical Formula 1] falls within the range of 21.3 to 22.2 ppm, and The peak based on the methyl group of the second unit in the three chains of propylene units represented by [mr] is in the range of 20.5 to 21.3 ppm, and the second unit in the three chains of propylene units represented by PPP [rr] The peak based on the methyl group of the eye appears in the range of 19.7 to 20.5 ppm.

  Here, PPP [mm], PPP [mr], and PPP [rr] are each represented by the following formula [Formula 1].

  Further, in the present invention, the propylene-based polymer has a partial structure (Ι) or (ΙΙ) of the following formula [Chem. 2] containing a regioregular unit based on 2,1-insertion and 1,3-insertion of propylene. Is contained in a specific amount.

It is believed that such a partial structure is caused by positional irregularities that occur during the polymerization of a propylene-based polymer, for example, when a polymerization reaction is performed using a metallocene-based catalyst.
That is, the propylene monomer usually reacts in a manner in which the methylene side is bonded to the metal component in the catalyst, that is, a so-called “1,2-insertion”. , 3-insertion ". “2,1-insertion” is a reaction type in which the addition direction is opposite to “1,2-insertion”, and forms a structural unit represented by the above partial structure (Ι) in a polymer chain.

  The term “1,3-insertion” means that a propylene monomer is incorporated into a polymer chain at C-1 and C-3, and as a result, a linear structural unit, that is, the above partial structure ( ΙΙ).

  A propylene-based polymer in which the proportion of each of the above-mentioned positionally irregular units is within the range of the requirement (b) can be obtained by selecting an appropriate catalyst. Specifically, for example, it can be obtained using a metallocene-based polymerization catalyst having a hydroazulenyl group as a ligand. Here, the metallocene-based polymerization catalyst is composed of a transition metal compound component having a metallocene structure and a promoter component. Although the proportion of each regio-irregular unit differs depending on the chemical structure of the metal complex component of the catalyst used for the polymerization, generally, the higher the polymerization temperature, the larger the tendency. In the present invention, the polymerization temperature is preferably from 0 to 80 ° C. in order to keep the proportion of each position irregular unit in the propylene-based polymer in the above-mentioned specific range.

The metal complex component can be used as it is as a catalyst component, but it can be used as a solid catalyst in which the above metal complex component is supported on an inorganic or organic fine-grained carrier that is a granular or fine solid. May be used.
When the metal complex component is supported on the fine particle carrier, the amount of the metal complex component supported is preferably 0.001 to 10 mmol, more preferably 0.001 to 5 mmol per 1 g of the carrier.

Among the above metallocene catalysts having a hydroazulenyl group as a ligand, catalysts using titanium, zirconium, and hafnium as metal atoms are preferable. Among them, complexes having zirconium are preferable because of high polymerization activity. .
Among the above metallocene catalysts, zirconium dichloride type complexes are preferably used, and among them, it is particularly preferable to use a crosslinked type complex.
Specifically, methylenebis {1,1 ′-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride, methylenebis {1,1 ′-(2-ethyl-4-phenyldihydroazulenyl)} zirconium dichloride , Methylenebis {1,1 '-(4-phenyldihydroazulenyl)} zirconium dichloride, methylenebis {1,1'-(4-naphthyldihydroazulenyl)} zirconium dichloride, ethylenebis {1,1 '-(2- Methyl-4-phenyldihydroazulenyl) zirconium dichloride, ethylenebis {1,1 ′-(2-ethyl-4-phenyldihydroazulenyl)} zirconium dichloride, ethylenebis {1,1 ′-(4-phenyldihydro (Azulenyl) zirconium dichloride, ethylenebis 1,1, '-(4 Naphthyldihydroazulenyl) {zirconium dichloride, isopropylidenebis} 1,1 ′-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride, isopropylidenebis {1,1 ′-(2-ethyl-4- Phenyldihydroazulenyl)｝ zirconium dichloride, isopropylidenebis ｛1,1 ′-(4-phenyldihydroazulenyl)｝ zirconium dichloride, isopropylidenebis ｛1,1 ′-(4-naphthyldihydroazulenyl)｝ zirconium dichloride , Dimethylsilylenebis {1,1 '-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride, dimethylsilylenebis {1,1'-(2-ethyl-4-phenyldihydroazulenyl)} zirconium dichloride , Dimethylsilylene bis {1,1 ′-(4-phenyldihydroazulenyl)} zirconium dichloride, dimethylsilylenebis {1,1 ′-(4-naphthyldihydroazulenyl)} zirconium dichloride, diphenylsilylenebis {1,1 ′-(2 -Methyl-4-phenyldihydroazulenyl) {zirconium dichloride, diphenylsilylenebis} 1,1 ′-(2-ethyl-4-phenyldihydroazulenyl)} zirconium dichloride, diphenylsilylenebis {1,1 ′-(4 -Phenyldihydroazulenyl) zirconium dichloride, diphenylsilylene bis {1,1 '-(4-naphthyldihydroazulenyl)} zirconium dichloride, and the like.
Among them, dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride and dimethylsilylenebis {1,1 ′-(2-ethyl-4-phenyldihydroazulene) are particularly preferable. (Nyl)｝ It is preferable to use zirconium dichloride. In this case, the proportion of each of the above-mentioned positional irregular units can be easily controlled within the range of the present invention, and the requirement (d) described later is satisfied (the isotactic triad fraction is 97%). The above-mentioned) propylene-based polymer can be obtained.

  Examples of the co-catalyst component include aluminoxanes such as methylaluminoxane, isobutylaluminoxane and methylisobutylaluminoxane; Lewis acids such as triphenylborane, tris (pentafluorophenyl) borane and magnesium chloride; and dimethylaniliniumtetrakis (pentafluorophenyl). And ionic compounds such as borate. It is also possible to use these cocatalyst components in combination with other organoaluminum compounds, for example, trialkylaluminums such as trimethylaluminum, triethylaluminum, and triisobutylaluminum.

  The mm fraction (isotactic triad fraction) in the entire polymer chain of the propylene-based polymer according to the present invention is expressed by the following [Equation 1]. By the way, in the partial structure (ΙΙ), as a result of 1,3-insertion, one methyl group derived from a propylene monomer has disappeared.

In this formula, ΣΙCH ₃ indicates the area of all methyl groups (all peaks at 19 to 22 ppm of chemical shift). A <1>, A <2>, A <3>, A <4>, A <5>, A <6>, A <7>, A <8>, and A <9> are The peak areas at 42.3 ppm, 35.9 ppm, 38.6 ppm, 30.6 ppm, 36.0 ppm, 31.5 ppm, 31.0 ppm, 37.2 ppm, and 27.4 ppm, and the partial structures (Ι) and (ΙΙ) ) Indicates the abundance ratio of carbon.
Further, the ratio of 2,1-inserted propylene and the ratio of 1,3-inserted propylene relative to the total propylene insertion were calculated by the following equations.

Next, in the present invention, the propylene polymer, the melting point of the polymer Tm [° C.], also the water vapor permeability at the shaping of the polymer into a film ^{Y [g / m 2 / 24hr} ] In this case, it is preferable that Tm and Y satisfy the following relational expression (1).
(−0.20) Tm + 35 ≦ Y ≦ (−0.33) Tm + 60 Equation (1)

The water vapor permeability can be measured according to JIS K7129 (1992), “Test Method for Water Vapor Permeability of Plastic Films and Sheets”. In this measurement, an infrared sensor method is employed as a test method, and a test temperature of 40 ± 0.5 ° C. and a relative humidity (90 ± 2)% RH are employed as test conditions.
The propylene-based polymer falling within the range of the above formula (1) shows a moderate water vapor permeability. The appropriate water vapor permeability promotes the penetration of the saturated steam used for molding into the foamed particles during the in-mold molding, thereby increasing the secondary foamability of the foamed particles, and as a result, between the foamed particles. The production of a shock absorber having no or few voids is facilitated.
As a method for producing the foamed particles, a method is generally used in which resin particles are dispersed in water, impregnated with a foaming agent, and then released from high temperature and high pressure to low pressure to form foamed particles. In this case, the appropriate water vapor permeability facilitates penetration of water and a foaming agent into the resin particles. As a result, the dispersion of the water and the foaming agent in the resin particles becomes uniform, the cell diameter of the foamed particles obtained becomes uniform, and the expansion ratio can be improved.
The water vapor permeability (Y) is expressed in relation to the melting point (Tm) of the propylene-based polymer because the foaming temperature during the production of foamed particles and the saturated steam temperature during in-mold molding are generally This is based on the fact that the higher the melting point (Tm) of the propylene polymer as the base resin, the higher the melting point (Tm), and the lower the melting point (Tm), the lower the melting point (Tm).

  When the water vapor permeability (Y) is lower than [(−0.20) · Tm + 35], the permeability of the water vapor and the foaming agent to the base resin becomes poor, and conversely, [(−0.33) ) .Tm + 60], the permeability of water vapor to the base resin becomes too good. In any case, the dispersion of water and the foaming agent in the resin particles during the production process of the foamed particles becomes uneven. And the uniformity of the cell diameter of the obtained expanded particles may be reduced. Further, the energy absorption efficiency of the impact absorbing material obtained by molding the expanded particles may be reduced. If the water vapor permeability (Y) exceeds [(−0.33) · Tm + 60], coarse bubbles may be mixed in the obtained foamed particles. Also in this case, there is a possibility that the energy absorption efficiency of the shock absorbing material obtained by molding the expanded particles may be reduced.

  A propylene-based polymer having a melting point (Tm) and a water vapor permeability (Y) satisfying the relationship of the formula (1) can be obtained by selecting an appropriate catalyst in producing the polymer. Specifically, among the above-mentioned metallocene-based catalysts, it can be suitably obtained by using bridged bis {1,1 '-(4-hydroazulenyl)} zirconium dichloride as a metal complex component. Preferred examples of such a metal complex component are as described above.

In the present invention, the melting point (Tm) of the propylene-based polymer is generally from 125 ° C to 165 ° C, preferably from 130 ° C to 160 ° C, and more preferably from 141 ° C to 158 ° C.
The melting point (Tm) described in JIS K7121 (1987) is used to determine the melting temperature after performing a certain heat treatment. , Each adopts 10 ° C. per minute), a DSC curve is drawn at a heating rate of 10 ° C. per minute using a heat flux DSC apparatus, and the top of the melting peak on the obtained DSC curve is adopted. If multiple peaks are observed, the peak with the highest melting peak is used based on the baseline on the high-temperature side. If there are multiple peaks with the highest melting peak, their arithmetic mean values are used. Is adopted.

  In general, the melting point (Tm) of the propylene-based polymer can be increased as the proportion of the structural units obtained from the comonomer is reduced and as the proportion of each of the irregular units is reduced.

The propylene-based polymer satisfying the requirements (a) and (b) and the formula (1) can be obtained using the metallocene-based catalyst.
In addition, the impact absorbing material of the present invention is obtained by filling foamed particles containing a propylene-based polymer having the above requirements (a) and (b) as a base resin into a molding die and foaming by heating. be able to.

Next, the propylene-based polymer preferably further has the following requirement (d) (claim 2).
(D) The isotactic triad fraction of 97% or more of the propylene unit chain portion composed of head-to-tail bonds measured by 13C-NMR.

  That is, in addition to the requirements (a) and (b) described above, a 13C-NMR (nuclear magnetic resonance method) ) Measured in the isotactic triad fraction (i.e., among three arbitrary propylene units in the polymer chain, each propylene unit is linked head-to-tail and the direction of methyl branch in the propylene unit is the same). (A ratio of three propylene units) is 97% or more.

  The isotactic triad fraction is hereinafter referred to as a mm fraction. When the mm fraction is 97% or more, the mechanical properties of the propylene-based polymer become higher. As a result, the mechanical properties and energy absorption efficiency of the shock absorbing material can be increased. Therefore, more preferably, the mm fraction is 98% or more.

Next, it is preferable that the propylene-based polymer further has the following requirement (e) (claim 3).
(E) The melt flow rate is 0.5 to 100 g / 10 minutes.

  In this case, the expanded particles used for obtaining the impact absorbing material can be produced while maintaining industrially useful production efficiency. Further, the mechanical properties and shock absorbing properties of the shock absorbing material can be improved.

  If the melt flow rate (MFR) is less than 0.5 g / 10 minutes, there is a possibility that the production efficiency of the foamed particles, particularly, the productivity in the melt-kneading step described below may be reduced. On the other hand, if it exceeds 100 g / 10 minutes, the mechanical properties such as the compressive strength and tensile strength of the shock absorbing material and the energy absorption efficiency may be reduced. Therefore, the MFR is more preferably 1.0 to 50 g / 10 minutes. More preferably, it is 1.0 to 30 g / 10 minutes. The above MFR means a melt mass flow rate measured according to the conditions described in Table 3 of JIS K6921-2 (1997).

Next, it is preferable that the foamed particles are foamed using a foaming agent satisfying the following requirement (f).
(F) When the critical temperature of the foaming agent is Tc [° C.], Tc is given by the following formula (2).
-90 ° C ≦ Tc ≦ 400 ° C Equation (2)
To be satisfied.

In this case, the bubble diameter of the expanded particles tends to be more uniform, and as a result, the mechanical properties of the shock absorber obtained by using the expanded particles are improved.
If Tc is less than -90 ° C, the resulting foamed particles will have significantly non-uniform cell diameters. The reason for this is not necessarily clear, but is presumed to be due to the rapid progress of foaming.
On the other hand, when the temperature exceeds 400 ° C., it may be extremely difficult to obtain expanded particles having a high magnification, for example, a density of 0.1 g / cm ³ or less.

  Specific examples of the foaming agent are as follows. The critical temperature (° C) is also described after the substance name. Chains of methane (-82), ethane (32), propane (97), butane (152), isobutane (135), pentane (197), hexane (235), cyclopentane (239), cyclohexane (280), etc. And halogenated hydrocarbons such as dichlorodifluoromethane (112) and trichloromonofluoromethane (198), and inorganic gases such as carbon dioxide (31).

Further, among the foaming agents satisfying the above formula (2), furthermore, the following formula (3)
0 ° C ≦ Tc ≦ 300 ° C Equation (3)
When the above conditions are satisfied, there is an advantage that no special equipment or device is required, especially when handling these foaming agents.

Furthermore, the following equation (4)
30 ° C ≦ Tc ≦ 200 ° C Equation (4)
If the above conditions are satisfied, in addition to the industrial utility described in the previous section, the foamed particles obtained will have extremely uniform cell diameters. This has the effect of being even better.
The above-mentioned foaming agents may be used alone or in combination with a plurality of foaming agents.

  Further, as the foaming agent, a so-called inorganic gas such as nitrogen, oxygen, air, carbon dioxide, and water is used as the foaming agent as a whole or as a main component (50 mol% or more of the entire foaming agent, preferably 70 mol% or more, more preferably Is 90 mol% or more.) When used, the energy absorption efficiency of the shock absorbing material can be increased. Among these inorganic gases, nitrogen, air, and carbon dioxide are particularly preferable in consideration of the stability of the apparent density of the expanded particles, the environmental load, the cost, and the like.

  In the present invention, as described above, other polymer components and additives can be mixed with the propylene-based polymer (base resin) as long as the effects of the present invention are not impaired.

  Examples of the other polymer component include ethylene resins such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene which is a copolymer of ethylene and an α-olefin (having 4 or more carbon atoms); polybutene resin; Ethylene-propylene rubber; Ethylene-propylene-diene rubber; hydrogenated block obtained by saturating at least a part of the ethylene-based double bond of styrene-diene block copolymer or styrene-diene block copolymer by hydrogenation Styrene-based thermoplastic elastomers such as copolymers; and graft-modified products of these resins, elastomers or rubbers with acrylic acid-based monomers. In the present invention, these resins, elastomers, rubbers or modified products thereof can be used alone or in combination of two or more.

  As the above additives, various additives such as a foam nucleating agent, a coloring agent, an antistatic agent, a lubricant and the like can be added. These are usually added together at the time of melt kneading described later and contained in the resin particles.

  Examples of the foam nucleating agent include inorganic compounds such as talc, calcium carbonate, silica, titanium oxide, gypsum, zeolite, borax, zinc borate, and aluminum hydroxide, as well as carbon, phosphoric acid nucleating agents, and phenolic nucleating agents. And organic nucleating agents such as amine nucleating agents. The amount of these various additives varies depending on the purpose of addition, but is not more than 15 parts by weight, preferably not more than 8 parts by weight, and most preferably not more than 5 parts by weight based on 100 parts by weight of the base resin.

  The mixing of the other polymer components and additives with the base resin can be performed by liquid mixing or solid mixing, but generally, melt kneading is used. That is, using a kneader such as a roll, a screw, a Banbury mixer, a kneader, a blender, or a mill, the above-mentioned base resin and other components are kneaded at a desired temperature, and after kneading, the production of expanded particles is performed. Into resin particles of a suitable size.

  After the above resin particles are melted and kneaded in the extruder, the kneaded material is extruded in a string form from a die having a fine hole attached to the tip of the extruder, and cut into a specified weight or size by a cutting machine equipped with a take-off machine. Can be obtained by any method.

  Generally, if the weight of one resin particle is 0.1 to 20 mg, there is no problem in the production of foamed particles. When the weight of one resin particle is in the range of 0.2 to 10 mg and the variation in the weight between the particles is small, the production of the expanded particles becomes easy, and the density variation of the obtained expanded particles becomes small. In addition, the filling property of the foamed particles into the mold and the like becomes good. As a result, the resulting shock absorbing material has a good surface condition and excellent shock absorbing properties.

  As a method of obtaining foamed particles from the resin particles, a method of impregnating the resin particles prepared as described above with a volatile foaming agent and then heating and foaming the resin particles, specifically, for example, Japanese Patent Publication No. Sho 49-2183 And JP-A-56-1344, West German Unexamined Patent Publication No. 1285722, and 2107683.

  That is, first, resin particles are put together with a dispersion medium and a volatile foaming agent in a pressure vessel that can be closed and opened, and heated to a temperature higher than the softening temperature of the base resin, and the resin particles are impregnated with the volatile foaming agent. Thereafter, the contents in the closed container are discharged from the closed container to a low-pressure atmosphere, whereby foamed particles can be obtained. Usually, after that, it is subjected to drying treatment and then subjected to in-mold molding.

In the above method, if the decomposable foaming agent is kneaded in the resin particles in advance, the foamed particles can be obtained without compounding the foaming agent in the pressure vessel.
As the decomposable foaming agent, any one that decomposes at the foaming temperature of the resin particles to generate gas can be used. Specific examples include sodium bicarbonate, ammonium carbonate, azide compounds, azo compounds and the like.

  It is preferable to use water, alcohol, or the like as the dispersion medium. Furthermore, water-soluble inorganic substances such as aluminum oxide, tribasic calcium phosphate, magnesium pyrophosphate, zinc oxide, kaolin talc, mica, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, etc., so that the resin particles are uniformly dispersed in the dispersion medium. It is preferable to use an anionic surfactant such as a water-soluble polymer-based protective colloid agent, sodium dodecylbenzenesulfonate, sodium alkanesulfonate alone or as a mixture of two or more.

Further, a dispersion enhancer that enhances the dispersing power of the dispersant (prevents fusion of the resin particles in the container even when the amount of the dispersant is reduced) may be added to the dispersion medium. In particular, when producing low-expanded foamed particles having an apparent density of 100 g / L or more, it is preferable to use a dispersion enhancer.
As such a dispersion enhancer, an inorganic substance which can be dissolved in at least 1 mg or more in 100 cc of water at 40 ° C. and in which at least one of the anion and cation of the compound is divalent or trivalent, is used. be able to. Examples of such an inorganic substance include magnesium chloride, magnesium nitrate, magnesium sulfate, aluminum chloride, aluminum nitrate, aluminum sulfate, iron chloride, iron sulfate, and iron nitrate.

  When releasing resin particles into a low-pressure atmosphere, in order to facilitate the release, the same inorganic gas or volatile foaming agent as described above is introduced into the closed container from outside to keep the pressure in the closed container constant. It is preferable to hold.

  Next, the above-mentioned shock-absorbing material is a first DSC curve obtained when 2 to 4 mg of a test piece cut from the shock-absorbing material is heated to 220 ° C. at a rate of 10 ° C./min by a differential scanning calorimeter. In addition, it is preferable to have a crystal structure in which an intrinsic peak and a high-temperature peak appear as endothermic peaks (claim 5). At this time, heating by the differential scanning calorimeter is started from normal temperature (20 to 45 ° C.).

That is, this means that the impact absorbing material forms a portion showing an endothermic peak (inherent peak) unique to the base resin and a portion showing an endothermic peak higher than that in the DSC curve. Means
In this case, the effect of improving the rigidity of the shock absorbing material can be obtained.

As described above, the impact absorbing material in which a unique peak and a high-temperature peak appear in the DSC curve is prepared in advance by forming expanded particles in which the unique peak and the high-temperature peak appear in the DSC curve, and forming the expanded particles by a molding method described later. Can be obtained by molding.
Expanded particles in which an endothermic peak (high-temperature peak) higher than that in addition to an endothermic peak (intrinsic peak) specific to the base resin in the DSC curve are described in, for example, JP-A-2002-200635. It can be produced by a method, and can be obtained by controlling the conditions for foaming the resin particles, specifically, the temperature, pressure, time, etc., until the resin particles are released into a low-pressure atmosphere.

  When the above-mentioned foamed particles are molded to produce the above-mentioned shock absorbing material, it can be molded using molding dies under various conditions. For example, after filling the above-mentioned foamed particles into a cavity composed of a pair of cavities and depressions under atmospheric pressure or reduced pressure, the cavities are compressed so as to reduce the cavity volume by 5 to 70%, and then a heat medium such as steam. Is introduced into the cavity, and the foamed particles are heated and fused to each other (for example, Japanese Patent Publication No. 46-38359).

  In addition, the foaming particles are preliminarily treated with one or more of a volatile foaming agent or an inorganic gas to increase the secondary foaming power of the foamed particles, and then, while maintaining the secondary foaming power, under atmospheric pressure or reduced pressure. There is also a pressure aging molding method in which after expanding foamed particles into a cavity formed by a pair of concave and convex molds, a heating medium is introduced into the mold cavity to heat and fuse the foamed particles. 22951).

  Also, after filling the foamed particles pressurized above the atmospheric pressure into the mold cavity pressurized by the compressed gas or more, the heating medium such as steam is introduced into the mold cavity to remove the foamed particles. There is also a compression filling molding method in which heat fusion is performed (for example, Japanese Patent Publication No. 4-46217).

  Furthermore, the foamed particles are filled into a cavity composed of a pair of dies under atmospheric pressure or reduced pressure by using foamed particles having a high secondary foaming power obtained under special conditions. There is also a normal pressure filling molding method in which a heating medium such as steam is introduced into the inside and the foamed particles are heated and fused (for example, Japanese Patent Publication No. 6-49795). It can also be formed by a combination of the above methods (for example, see Japanese Patent Publication No. Hei 6-22919).

Further, the density of the shock absorbing material is preferably 0.02 to 0.45 g / cm ³ .
In this case, both sufficient energy absorption performance and light weight can be achieved.

If the density of the shock absorbing material is less than 0.02 g / cm ³ , the energy absorbing performance may be insufficient.
On the other hand, when it exceeds 0.45 g / cm ³ , there is a possibility that the lightweight property which is an excellent feature of the foam is not sufficiently exhibited.
In addition, the density of the shock absorbing material means an apparent overall density defined by JIS K7222 (1999).

  The impact absorbing material can be used, for example, as a core material of an automobile bumper, a core material of an automobile interior material, and the like. Here, examples of the automobile interior material include a dashboard, a console box, an instrument panel, a door panel, a door trim, a ceiling material, an interior material of a pillar portion, a sun visor, an armrest, and a headrest.

Further, it is preferable that the shock absorbing material has a skin layer having a higher density on the surface than the inside thereof.
In this case, the strength of the shock absorbing material, particularly the bending strength, can be further improved. Therefore, the impact absorbing material can be suitably used as a core material of an automobile bumper, an automobile interior material, and the like.

The skin layer can be integrally formed when the foamed particles are molded in a mold such as a mold to produce a shock absorbing material.
For example, the skin layer can be formed by partially melting the foamed particles by heat at a portion which has been in contact with the mold wall of the mold when the foamed particles are molded in the mold. Therefore, the components of the skin layer are the same as those of the expanded particles.

Preferably, the shock absorbing material is a core material of an automobile bumper.
In this case, the excellent shock absorbing characteristics of the shock absorbing material can be used to the maximum.

  Next, in the second invention (claim 9), the present invention relates to a shock absorber having a skin material provided on the surface of the shock absorber, and the skin material is, for example, a polyolefin elastomer sheet, OPS (2). (Polyaxially oriented polystyrene sheet), polystyrene resin film such as high heat resistant OPS and HIPS, polypropylene resin film such as CPP (unstretched polypropylene film), OPP (biaxially oriented polypropylene film) or polyethylene resin film, polyester Various films, such as resin films, and various skin materials, such as felt and nonwoven fabric, are mentioned. When the above-mentioned skin material is used as a skin (fascia) of an automobile bumper, an injection-molded article made of a polyolefin elastomer, impact-resistant polypropylene, or the like can be used as the skin material.

  The thickness of the skin material is not limited, but is usually 15 μm to 4000 μm. These skin materials may be painted or printed as necessary. Further, the skin material may be integrated with the shock absorbing material by fitting, but it is preferable that both are integrated by bonding. When both are bonded and integrated, mechanical strength, particularly bending strength, can be increased. The bonding and integration may be performed simultaneously with the heat fusion molding (in-mold molding) of the expanded particles. Further, a skin material may be bonded and integrated by post-processing to a shock absorbing material obtained by molding in a mold in advance. In addition, bonding and integration can be performed using a hot-melt adhesive as needed.

  The shock absorber can be used, for example, in an automobile bumper (claim 10), and can also be used as an automobile interior material or the like. Here, examples of the automobile interior material include a dashboard, a console box, an instrument panel, a door panel, a door trim, a ceiling material, an interior material of a pillar portion, a sun visor, an armrest, and a headrest. When used for an automobile bumper, it can be used as a core material of the above-described automobile bumper or as a bumper component in which a facer is integrated with the core material of the automobile bumper. In this case, the excellent shock absorbing properties and strength of the shock absorber can be utilized to the maximum.

  Next, embodiments of the present invention will be described.

[Production of propylene-based polymer]
First, a propylene-based polymer as a base resin for the expanded particles was synthesized by the methods shown in Production Examples 1 to 8 below.

Production Example 1
(I) Synthesis of [dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyl-4-hydroazulenyl)} zirconium dichloride] The following reactions were all carried out in an inert gas atmosphere. A dried and purified solvent was used.

(A) Synthesis of racemic-meso mixture 2.22 g of 2-methylazulene synthesized according to the method described in JP-A-62-207232 was dissolved in 30 mL of hexane, and 15.6 mL of a cyclohexane-diethyl ether solution of phenyllithium (15.6 mL). 1.0 eq) at 0 ° C. in small portions.
The solution was stirred at room temperature for 1 hour, cooled to -78 ° C, and 30 mL of tetrahydrofuran was added.

  Next, after adding 0.95 mL of dimethyldichlorosilane, the temperature was raised to room temperature, and the mixture was further heated at 50 ° C. for 90 minutes. Thereafter, a saturated aqueous solution of ammonium chloride was added, the organic layer was separated, dried over sodium sulfate, and the solvent was distilled off under reduced pressure.

The resulting crude product was purified by silica gel column chromatography (hexane-: dichloromethane = 5: 1) to give bis {1,1 '-(2-methyl-4-phenyl-1,4-dihydroazulenyl). 1.) 1.48 g of dimethylsilane were obtained.
786 mg of bis {1,1 ′-(2-methyl-4-phenyl-1,4-dihydroazulenyl) dimethylsilane obtained above is dissolved in 15 mL of diethyl ether, and n-butyllithium hexane is added at −78 ° C. 1.98 mL of a solution (1.68 mol / L) was added dropwise, and the temperature was gradually raised to room temperature, followed by stirring at room temperature for 12 hours. The solid obtained by evaporating the solvent under reduced pressure was washed with hexane and dried under reduced pressure.

Further, 20 mL of a toluene-diethyl ether mixed solvent (40: 1) was added, 325 mg of zirconium tetrachloride was added at -60 ° C, and the mixture was gradually heated and stirred at room temperature for 15 minutes.
The obtained solution is concentrated under reduced pressure, and hexane is added to cause reprecipitation, whereby dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyl-4-hydroazulenyl)} zirconium dichloride is obtained. / Meso mixture 150 mg was obtained.

(B) Separation of a racemic body 887 mg of a racemic / meso mixture obtained by repeating the above reaction was placed in a glass container, dissolved in 30 mL of dichloromethane, and irradiated with light from a high-pressure mercury lamp for 30 minutes. Thereafter, dichloromethane was distilled off under reduced pressure to obtain a yellow solid.
To this solid, 7 mL of toluene was added, stirred, and allowed to stand, whereby a yellow solid was separated as a precipitate. The supernatant was removed, and the solid was dried under reduced pressure to give 437 mg of a racemate comprising dimethylsilylenebis {1,1 '-(2-methyl-4-phenyl-4-hydroazulenyl)} zirconium dichloride.

(Ii) Synthesis of catalyst (a) Treatment of catalyst carrier 135 mL of demineralized water and 16 g of magnesium sulfate were placed in a glass container, and stirred to form a solution. 22.2 g of montmorillonite ("Kunipia-F" manufactured by Kunimine Industries) was added to this solution, and then the temperature was raised and the temperature was maintained at 80 ° C for 1 hour.
Then, after adding 300 mL of demineralized water, the solid content was separated by filtration. After adding 46 mL of demineralized water, 23.4 g of sulfuric acid, and 29.2 g of magnesium sulfate to the solid content, the mixture was heated, treated with heating under reflux for 2 hours, added with 200 mL of demineralized water, and filtered.
Further, an operation of adding 400 mL of deionized water and filtering was performed twice. Thereafter, the solid was dried at 100 ° C. to obtain a chemically treated montmorillonite as a catalyst carrier.

(B) Preparation of catalyst component After sufficiently replacing the inside of a 1-liter stirred autoclave with propylene, 230 mL of dehydrated heptane was introduced, and the system temperature was maintained at 40 ° C.
Here, 10 g of the chemically treated montmorillonite as a catalyst carrier prepared above was suspended in 200 mL of toluene and added.

  Furthermore, racemic (0.15 mmol) of dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyl-4-hydroazulenyl)} zirconium dichloride and triisobutylaluminum (3 mmol) prepared in separate containers. Was mixed in toluene (20 mL in total) and added to the autoclave.

  Thereafter, propylene was introduced at a rate of 10 g / hr for 120 minutes, and thereafter the polymerization reaction was continued for 120 minutes. Thereafter, the solvent was distilled off and dried under a nitrogen atmosphere to obtain a solid catalyst component. This catalyst component contained 1.9 g of polymer per 1 g of solid component.

(Iii) Polymerization of propylene (propylene homopolymerization)
After sufficiently replacing the inside of a stirred autoclave having an internal volume of 200 L with propylene, 45 kg of sufficiently dehydrated liquefied propylene was introduced. To this, 500 mL (0.12 mol) of a hexane solution of triisobutylaluminum and hydrogen (3NL) were introduced, and the inside of the autoclave was heated to 70 ° C.
Thereafter, the solid catalyst component (1.7 g) was press-injected with argon to start polymerization, and a polymerization reaction was performed for 3 hours.

Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the remaining gas components were purged to obtain 14.1 kg of a polymer.
This polymer has 100 mol% of structural units obtained from propylene, that is, it is a propylene homopolymer. This satisfies the requirement (a).

This polymer had an MFR (melt flow rate) of 10 g / 10 min, an isotactic triad fraction of 99.7%, and was measured by the DSC method (however, the temperature was raised from 30 ° C. at a rate of 10 ° C./min). The melting point is 146 ° C., which satisfies the requirements (d) and (e). Furthermore, the ratio of the position irregular units based on the 2,1-insertion is 1.32%, and the ratio of the position irregular units based on the 1,3-insertion is 0.08%, which satisfies the requirement (b). I have.
Hereinafter, the obtained polymer is referred to as “polymer 1”.

(Iv) Measurement of Water Vapor Permeability The polymer 1 obtained above was formed into a film having a thickness of 25 μm, and the water vapor permeability Y was measured according to the method described in JIS K7129 (the same applies to the following production examples). It was ^{10.5 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of this polymer 1 is 146 ° C., Y should be within the range of 5.8 ≦ Y ≦ 11.8 from the above formula (1), but was within the range.

Production Example 2 (propylene homopolymerization)
After sufficiently replacing the inside of a stirred autoclave having an internal volume of 200 L with propylene, 45 kg of sufficiently dehydrated liquefied propylene was introduced. To this, 500 mL (0.12 mol) of a hexane solution of triisobutylaluminum and hydrogen (3 NL) were introduced, and the inside of the autoclave was heated to 40 ° C.
Thereafter, the solid catalyst component (3.0 g) was injected with argon to start polymerization, and a polymerization reaction was performed for 3 hours.

Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the remaining gas components were purged to obtain 4.4 kg of a polymer.
This polymer has 100 mol% of structural units obtained from propylene, that is, it is a propylene homopolymer. This satisfies the requirement (a).

This polymer had an MFR of 2 g / 10 min, an isotactic triad fraction of 99.8%, and a melting point of 152 measured by the DSC method (however, the temperature was raised from 30 ° C. at a rate of 10 ° C./min). ° C, and satisfies the above requirements (d) and (e). Further, the ratio of the position irregular units based on the 2,1-insertion is 0.89%, and the ratio of the position irregular units based on the 1,3-insertion is 0.005%, which satisfies the requirement (b). I have.
Hereinafter, the obtained polymer is referred to as “polymer 2”.

As for the polymer 2, as in the polymer 1 was examined the water vapor transmission rate Y when molded into a film was ^{9.5 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of the polymer 2 is 152 ° C., from the above formula (1), Y should be within the range of 4.6 ≦ Y ≦ 9.8, but was within the range.

Production Example 3 (propylene / ethylene copolymerization)
After sufficiently replacing the inside of a 200 L stirred autoclave with propylene, 60 L of purified n-heptane was introduced, 500 mL (0.12 mol) of a hexane solution of triisobutylaluminum was added, and the inside of the autoclave was heated to 70 ° C. Warmed up. Thereafter, the solid catalyst component (9.0 g) was added, and a mixed gas of propylene and ethylene (propylene: ethylene = 97.5: 2.5; weight ratio) was introduced so that the pressure became 0.7 MPa. To initiate polymerization, and a polymerization reaction was carried out under these conditions for 3 hours.

Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the remaining gas components were purged to obtain 9.3 kg of a polymer.
This polymer contains 97.0 mol% of structural units obtained from propylene and 3.0 mol% of structural units obtained from ethylene. This satisfies the requirement (a).

This polymer had an MFR of 14 g / 10 min, an isotactic triad fraction of 99.2%, and a melting point of 141 measured by the DSC method (however, the temperature was raised from 30 ° C. at a rate of 10 ° C./min). ° C, and satisfies the above requirements (d) and (e). Further, the ratio of the position irregular units based on the 2,1-insertion is 1.06%, and the ratio of the position irregular units based on the 1,3-insertion is 0.16%, which satisfies the requirement (b). I have.
Hereinafter, the obtained polymer is referred to as “polymer 3”.

Further, the polymer 3, in the same manner as in the polymer 1 was examined the water vapor transmission rate Y when molded into a film was ^{12.0 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of this polymer 3 is 141 ° C., Y should be within the range of 6.8 ≦ Y ≦ 13.5 from the above formula (1), but was within the range.

Production Example 4 (Propylene / 1-butene copolymerization)
After sufficiently replacing the inside of a 200 L stirred autoclave with propylene, 60 L of purified n-heptane was introduced, 500 mL (0.12 mol) of a hexane solution of triisobutylaluminum was added, and the inside of the autoclave was heated to 70 ° C. Warmed up. Thereafter, the solid catalyst component (9.0 g) was added, and a mixed gas of propylene and 1-butene (propylene: 1-butene = 90: 10; weight ratio) was introduced so that the pressure became 0.6 MPa. To initiate polymerization, and a polymerization reaction was carried out under these conditions for 3 hours.

Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the remaining gas components were purged to obtain 8.6 kg of a polymer.
This polymer contains 95.4 mol% of a structural unit obtained from propylene and 4.6 mol% of a structural unit obtained from 1-butene. This satisfies the requirement (a).

This polymer had an MFR of 6 g / 10 min, a melting point of 142 ° C. measured by the DSC method (however, the temperature was raised from 30 ° C. at a rate of 10 ° C./min), and an isotactic triad fraction of 99.3%. And satisfies the above requirements (d) and (e). Furthermore, the ratio of the position irregular units based on the 2,1-insertion is 1.23%, and the ratio of the position irregular units based on the 1,3-insertion is 0.09%, which satisfies the requirement (b). I have.
Hereinafter, the obtained polymer is referred to as “polymer 4”.

Further, the polymer 4, as well as polymer 1, were examined water vapor transmission rate Y when molded into a film was ^{11.5 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of this polymer 4 is 142 ° C., Y should be within the range of 6.6 ≦ Y ≦ 13.1.

Production Example 5 (propylene homopolymerization)
After sufficiently replacing the inside of a 200 L stirred autoclave with propylene, 60 L of purified n-heptane was introduced, and 11.5 g of diethylaluminum chloride (45 g) and a titanium trichloride catalyst manufactured by Marubeni Solvay Co., Ltd. were placed in a propylene atmosphere. Introduced. Further, while maintaining the hydrogen concentration in the gas phase at 7.0% by volume, propylene was introduced into the autoclave at an internal temperature of 65 ° C. at a rate of 9 kg / hr for 4 hours.

After stopping the introduction of propylene, the reaction was further continued for 1 hour, the reaction was stopped by adding 100 mL of butanol to the reaction system, and the remaining gas components were purged to obtain 30 kg of a polymer.
This polymer has 100 mol% of structural units obtained from propylene, that is, it is a propylene homopolymer. This satisfies the requirement (a).

This polymer had an MFR of 10 g / 10 min, a melting point of 160 ° C. measured by the DSC method (however, the temperature was raised from 30 ° C. at a rate of 10 ° C./min), and an isotactic triad fraction of 97.0%. there were.
In this polymer, the ratio of the positionally irregular units based on the 2,1-insertion was 0%, and the ratio of the positionally irregular units based on the 1,3-insertion was 0%. That is, it does not satisfy the requirement (b).
Hereinafter, the obtained polymer is referred to as “polymer 5”.

This polymer 5, as in the polymer 1 was examined the water vapor transmission rate Y when molded into a film was ^{10.0 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of this polymer 5 is 160 ° C., Y should be within the range of 3.0 ≦ Y ≦ 7.2 from the above formula (1), but was not within the range.

Production Example 6 (propylene / ethylene copolymerization)
After sufficiently replacing the inside of a 200 L stirred autoclave with propylene, 60 L of purified n-heptane was introduced, and diethyl aluminum chloride (40 g) and 7.5 g of Marubeni Solvay's titanium trichloride catalyst were placed in a propylene atmosphere. Introduced. Further, while maintaining the hydrogen concentration in the gas phase at 7.0% by volume, a mixed gas of propylene and ethylene (propylene: ethylene = 97.5: 2.5; weight ratio) was applied at an internal temperature of the autoclave of 60 ° C. The pressure was introduced so as to be 0.7 MPa.

After stopping the introduction of the mixed gas, the reaction was further continued for 1 hour, the reaction was stopped by adding 100 mL of butanol to the reaction system, and the residual gas component was purged to obtain 32 kg of a polymer.
This polymer contains 96.1 mol% of structural units obtained from propylene and 3.9 mol% of structural units obtained from ethylene. This satisfies the requirement (a).

This polymer had an MFR of 12 g / 10 min, a melting point of 146 ° C. measured by the DSC method (however, the temperature was raised from 30 ° C. at a rate of 10 ° C./min), and an isotactic triad fraction of 96.0%. Met.
In this polymer, the ratio of the positionally irregular units based on the 2,1-insertion was 0%, and the ratio of the positionally irregular units based on the 1,3-insertion was 0%. That is, it does not satisfy the requirement (b).
Hereinafter, the polymer obtained here is referred to as “polymer 6”.

Further, for the above polymer 6, in the same manner as in the polymer 1 was examined the water vapor transmission rate Y when molded into a film was ^{15.0 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of this polymer 6 is 146 ° C., from the above formula (1), Y should be within the range of 5.8 ≦ Y ≦ 11.8, but was not within the range.

Production Example 7 (propylene homopolymerization)
The method was carried out by applying the method described in [Production of base resin 1] in the examples of JP-A-6-240041.
That is, after thoroughly replacing the inside of a 200 L stirred autoclave with propylene, 60 L of purified n-heptane was introduced, and 120 g of methylalumoxane (average degree of oligomer 16) manufactured by Tosoh Akzo Co., Ltd. was used. Rac-Dimethylsilylenebis (2-methylindenyl) zirconium dichloride (150 mg) synthesized by the method described in Japanese Patent No. 268307 was introduced in a propylene atmosphere. Further, while maintaining the hydrogen concentration in the gas phase at 0.5% by volume, propylene was introduced into the autoclave at an internal temperature of 40 ° C. at a rate of 7 kg / hr for 3 hours.

After stopping the introduction of propylene, the reaction was further continued for 1 hour, the reaction was stopped by adding 100 mL of butanol to the reaction system, and the residual gas component was purged to obtain 9.4 kg of a polymer.
This polymer has 100 mol% of structural units obtained from propylene, that is, it is a propylene homopolymer. This satisfies the requirement (a). Hereinafter, the obtained polymer is referred to as “polymer 7”.

This polymer 7 had an MFR = 9, a melting point (Tm) of 150 ° C., an isotactic triad fraction of 94.4%, a proportion of positional irregular units based on 2,1-insertion of 0.25%, and 1,1. 3- The proportion of regio-irregular units due to insertion was below the detection limit, ie less than 0.005%. That is, this one does not satisfy the requirement (b).
In Table 2, which will be described later, the ratio of the position irregular units based on the 1,3 insertion of the polymer 7 is shown as 0%.

Also, for the polymer 7, in the same manner as in the above polymers 1 to 6, were examined water vapor transmission rate Y after molding into a film was ^{4.8 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of this polymer 7 is 150 ° C., Y should be within the range of 5.0 ≦ Y ≦ 10.5 from the above formula (1), but it was outside the range.

Production Example 8 (Homopolymerization of propylene)
After sufficiently replacing the inside of a 200 L stirred autoclave with propylene, 60 L of purified n-heptane was introduced, and 120 g of methylalumoxane (average degree of oligomer: 16) manufactured by Tosoh Akzo Co., Ltd. was used. H. Yamazaki et al., "Chemistry Letters", Japan, 1989, Vol. 18, p. 1853], rac-dimethylsilylenebis (3-methylcyclopentadienyl) zirconium dichloride (100 mg) was introduced under a propylene atmosphere. Further, while maintaining the hydrogen concentration in the gas phase at 0.5% by volume, propylene was introduced into the autoclave at an internal temperature of 40 ° C. at a rate of 7 kg / hr for 3 hours.

After stopping the introduction of propylene, the reaction was further continued for 1 hour, the reaction was stopped by adding 100 mL of butanol to the reaction system, and the residual gas component was purged to obtain 5.6 kg of a polymer.
This polymer has 100 mol% of structural units obtained from propylene, that is, it is a propylene homopolymer. This satisfies the requirement (a). Hereinafter, the obtained polymer is referred to as “polymer 8”.

This polymer 8 has an MFR = 20, a melting point of 141 ° C., an isotactic triad fraction of 91.5%, a proportion of regiorandom units based on 2,1-insertion of 2.1%, and 1,3-insertion. Was 0.45%.
That is, this one does not satisfy the requirement (b).

Also, for the polymer 8, in the same manner as in the polymer 1 was examined the water vapor transmission rate Y after molding into a film was ^{13.8 (g / m 2 / 24hr} ).
In addition, since the melting point Tm of this polymer 8 is 141 ° C., from the above formula (1), Y should be within the range of 6.8 ≦ Y ≦ 13.5, but was out of the range.

  Tables 1 and 2 show the results of Production Examples 1 to 8 described above.

As can be seen from Table 1, Polymer 1 to Polymer 4 satisfy the above requirements (a) and (b) and correspond to the propylene-based polymer as the base resin in the present invention. Polymers 1 to 4 also satisfy the above formula (1) and the above requirements (d) and (e).
On the other hand, as can be seen from Table 2, Polymers 5 to 8 satisfy the above requirement (a) but do not satisfy the above requirement (b). Further, Polymer 5 to Polymer 8 do not satisfy the above formula (1).

  Next, Examples 1 to 4 and Comparative Examples 1 to 4 in which impact absorbing materials were produced using the polymers 1 to 8 obtained in the above Production Examples 1 to 8 will be described.

Example 1
As shown in FIGS. 1 and 2, the shock absorber 1 of this embodiment has a substantially U-shaped cross section in a plane perpendicular to the longitudinal direction, and is formed for a core material of an automobile bumper.
The shock absorber 1 has a high-density skin layer 15 so as to cover the surface.
Hereinafter, a method of manufacturing the shock absorbing material 1 will be described.

First, foamed particles to be used as the material of the shock absorbing material are prepared as follows.
Propylene homopolymer (Polymer 1) as a base resin obtained in Production Example 1 was added to an antioxidant (0.05 wt% of "Yoshinox BHT" manufactured by Yoshitomi Pharmaceutical Co., Ltd. and "Irganox" manufactured by Ciba Geigy. 1010 "(0.10 wt%), and extruded into a strand having a diameter of 1 mm using a 65 mmφ single screw extruder, cooled in a water bath, and cut into a length of 2 mm to obtain fine-grained pellets.

  1000 g of the pellet was put in a 5 liter autoclave together with 2500 g of water, 200 g of tribasic calcium phosphate and 0.2 g of sodium dodecylbenzenesulfonate, 85 g of isobutane was added, and the temperature was raised to 135 ° C. for 60 minutes. For 30 minutes.

Thereafter, the valve at the bottom of the autoclave was opened and the contents were discharged to the atmosphere while compressed nitrogen gas was externally added to maintain the pressure in the autoclave at a gauge pressure of 2.3 MPa.
After drying the foamed particles obtained by the above operation, the bulk density was measured and found to be 48 g / L. Further, the cells of the expanded particles had an average of 310 μm and were very uniform.

  The average cell diameter of the foamed particles can be obtained by observing a cross-section of the foamed particles cut through the center of a randomly selected foamed particle with a microscope or by displaying this cross-section on the screen. In the projection, 50 bubbles were randomly selected, the diameter (maximum length) of each bubble was measured, and the average value was shown.

Next, the foamed particles obtained as described above were molded to produce the shock absorbing material 1 shown in FIGS.
Specifically, after filling the foamed particles into the cavity of the aluminum mold, the mold chamber is steamed at a gauge pressure of 0.28 MPa (shown as "molding vapor pressure" in Table 3) into the mold chamber. By molding, an impact absorbing material 1 shown in FIG. 1 was obtained.
At this time, in the portion where the foamed particles come into contact with the mold, the foamed particles are partially fused and fused to each other, and as shown in FIG. The high-density skin layer 15 was formed.
The shock absorbing material 1 had an internal density (a part other than the skin layer) of 60 g / L, a small gap on the surface, and an excellent surface appearance with no irregularities.

Further, the impact absorbing material 1 was broken from the center and the fusion degree of the cross section was measured to be 80%.
The degree of fusion was measured by visually observing the number of particle destruction and the number of interparticle destruction in the cross section of the shock absorbing material, and expressed as a ratio of the number of particle destruction to the total number of both. did.

  Also, a test piece having a length of 50 mm, a width of 50 mm and a thickness of 25 mm was prepared from the inner part (the part other than the skin layer) of another shock absorber 1 molded under the same molding conditions, and according to JIS K7220 (1999). A compression test was performed at a test piece temperature of 23 ° C. and a compression speed of 10 mm / min. Based on the results obtained here, a stress-strain diagram (an example of which is shown in FIG. 3) was created. From this figure, when the stress at the time of 50% compression (same as at the time of 50% strain) was obtained, it was 0.73 MPa in this example.

The energy absorption efficiency (%) was obtained by the following equation.
Energy absorption efficiency (%) = {(OAB area) / (OABC area)} × 100
That is, the energy absorption efficiency (%) is the area of the part surrounded by the line connecting the points O, A, and B (the area of the part shown by oblique lines in the figure) in the stress-strain diagram as shown in FIG. , Points O, A, B, and C divided by the area of the figure having the vertices as a percentage.

Further, using a test piece of the same size, the compression set was measured by the method described in JIS K6767 (1976), and it was 11%.
The results are shown in Table 3 below. In addition, the forming steam pressure in Table 3 means a steam pressure that gives a formed body (shock absorbing material) having a fusion degree of 80%.

(Examples 2 to 4) and (Comparative Examples 1 to 4)
Example 1 was carried out in the same manner as in Example 1 except that the above polymers 2 to 8 shown in Table 1 or Table 2 were used as the base resin.
The results are shown in Tables 3 and 4 below.

According to Table 3, in Examples 1 to 4 according to the present invention, a propylene-based polymer having the above requirements (a) and (b) was used as the base resin of the foamed particles. The shock absorbers obtained by molding all have a high degree of fusion despite being heated at a low molding vapor pressure, and the mechanical properties are also compressive strength (stress at 50% compression) and energy. It can be seen that the absorption efficiency is high and the compression set is small. Therefore, the shock absorbing materials of Examples 1 to 4 can be used as an excellent core material of an automobile bumper.
Further, as shown in FIGS. 1 and 2, the shock absorbers 1 of Examples 1 to 4 have a skin layer 15 on the surface. These shock absorbers 1 can also be used as automobile bumpers and the like.

  On the other hand, as shown in Table 4, when the polymer 5 or the polymer 6 not satisfying the requirement (b) obtained in the above-mentioned Production Example 5 or 6 is used as the base resin of the expanded particles, Impact-absorbing materials obtained by molding these expanded particles in a mold require a high molding vapor pressure during molding and have insufficient compressive strength (stress at 50% compression) and energy absorption efficiency. Further, the compression set was large relative to the compression strength (see Comparative Examples 1 and 2).

In Comparative Example 3 in which the polymer 7 was used as the base resin for the expanded particles, the shock absorbing material obtained by in-mold molding using the expanded particles had a compressive strength (stress at 50% compression). However, the compression set was large. Also, the energy absorption efficiency was insufficient.
Further, in Comparative Example 4 in which the polymer 8 was used as the base resin for the foamed particles, the impact absorbing material molded using the foamed particles had a small compression set, but a small compressive strength (stress at 50% compression). ) And the energy absorption efficiency was significantly reduced.

Production Example 1 and Production Example 2 show examples in which a propylene homopolymer was produced using the same metallocene polymerization catalyst, but the properties of the obtained propylene homopolymer were different. The reason for this is based on the difference in polymerization temperature. That is, in Production Example 1 having a higher polymerization temperature, the proportion of each position irregular unit in the propylene homopolymer obtained is higher.
Further, Production Examples 5 and 6 show examples in which no regioregular units were formed in the obtained propylene-based polymer by using a Ziegler / Natta catalyst different from the metallocene-based polymerization catalyst.

Production Example 7 shows an example in which a propylene homopolymer was produced using a metallocene-based polymerization catalyst different from that in Production Example 1. However, under the conditions described in the known literature, the ratio of each position irregular unit was not It can be seen that this is below the scope of the invention. In Production Example 7, the polymerization temperature was 40 ° C., but when the polymerization temperature was increased to, for example, 70 ° C. or higher, the propylene homopolymer obtained had a position irregular unit within the range of the present invention. However, the [mm] fraction is expected to be lower than that of the propylene homopolymer of Production Example 7.
Production Example 8 shows an example in which a propylene homopolymer was produced using a metallocene polymerization catalyst different from Production Examples 1 and 7, and the metal complex component of the metallocene polymerization catalyst used was not suitable. Therefore, the proportion of each position irregular unit exceeded the range of the present invention.

(Example 5)
This example is an example of manufacturing a shock absorber having a skin material on the surface of the shock absorber.
The shock absorber of the present embodiment is a dashboard of an automobile as shown in FIGS.

  Further, as shown in FIGS. 4 and 5, the shock absorber 3 has a skin material 37 so as to cover one surface of the shock absorber 35 formed into a plurality of uneven shapes. In this shock absorber 3, the shock absorber 35 is made of expanded polypropylene particles, and the skin material 37 is made of a polyolefin elastomer sheet.

Next, a method of manufacturing the shock absorber of the present embodiment will be described.
First, the same expanded particles as in Example 1 were prepared. The method for producing the expanded particles is the same as that in Production Example 1 and Example 1 described above.

Next, after the skin material was attached to one of the molds, the foamed particles were filled.
Next, of the middle dies attached to the two molds constituting the molding die, in the shock absorber shown in FIG. 5, a sheet for forming a skin material is formed on a mold (concave mold) forming the skin material 37 side. The mold was placed, the mold was clamped, and the above-mentioned mold was filled with foamed particles.
Thereafter, the mold was heated and formed into a chamber of a mold through steam having a gauge pressure of 0.28 MPa to obtain the shock absorber 3 shown in FIGS.
In the shock absorber 3, the density of the shock absorber 35 was 60 g / L, the surface gap was small, and the surface appearance without irregularities was excellent.

As shown in FIGS. 4 and 5, the shock absorber 3 is provided with a skin material 37 so as to cover one surface of the shock absorber 35 similar to the first embodiment.
Therefore, in the shock absorber 3, the shock absorber 35 absorbs the energy at the time of the shock as described above, and the skin material 37 provided on the surface of the shock absorber 35 is The effect of improving the strength of the shock absorber 3 and making the surface of the shock absorber 3 beautiful is shown.

FIG. 2 is an explanatory view showing the entire shock absorber according to the first embodiment. FIG. 2 is an explanatory cross-sectional view of the shock absorbing material according to the first embodiment. FIG. 3 is an explanatory diagram showing a stress-strain diagram of the shock absorbing material according to the first embodiment. FIG. 13 is an explanatory view showing the entire shock absorber according to the fifth embodiment. Sectional explanatory drawing of the shock absorber concerning Example 5. FIG.

Explanation of reference numerals

1. . . Shock absorber (Example 1)
15. . . Epidermis layer 3. . . Shock absorber 35. . . Shock absorber (Example 5)
37. . . Skin material

Claims (10)

A shock absorber made by molding foamed particles into a mold,
An impact-absorbing material, wherein the expanded particles comprise a propylene-based polymer having the following requirements (a) and (b) as a base resin.
(A) 100 to 85 mol% of structural units obtained from propylene, and 0 to 15 mol% of structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms (provided that propylene is obtained from propylene) The total amount of the structural units and the structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms is 100 mol%).
(B) The ratio of the position irregular units based on the 2,1-insertion of the propylene monomer unit in the total propylene insertion is 0.5 to 2.0%, and the ratio of the propylene monomer unit is 1%, as measured by 13C-NMR. , 3- The ratio of the position irregular units based on insertion is 0.005 to 0.4%. 2. The shock absorbing material according to claim 1, wherein the propylene polymer further has the following requirement (d).
(D) The isotactic triad fraction of 97% or more of the propylene unit chain portion composed of head-to-tail bonds measured by 13C-NMR. 3. The shock absorbing material according to claim 1, wherein the propylene-based polymer further has the following requirement (e).
(E) The melt flow rate is 0.5 to 100 g / 10 minutes. The shock absorber according to any one of claims 1 to 3, wherein the foamed particles are foamed using a foaming agent satisfying the following requirement (f).
(F) When the critical temperature of the foaming agent is Tc [° C.], Tc satisfies the following expression (2).
-90 ° C ≦ Tc ≦ 400 ° C Equation (2)   5. The shock absorbing material according to claim 1, wherein 2 to 4 mg of a test piece cut from the shock absorbing material is heated to 220 ° C. at a rate of 10 ° C./min by a differential scanning calorimeter. A shock absorber characterized in that it has a crystal structure in which an intrinsic peak and a high-temperature peak appear as endothermic peaks in the first DSC curve obtained in (1). According to any one of claims 1 to 5, density of the shock absorber is a shock absorber which is a 0.02~0.45g / cm ^3.   The shock absorber according to any one of claims 1 to 6, wherein the shock absorber has a higher density skin layer on its surface than inside.   The shock absorber according to any one of claims 1 to 7, wherein the shock absorber is a core material of an automobile bumper.   A shock absorber comprising a surface material provided on a surface of the shock absorber according to any one of claims 1 to 8.   10. The shock absorber according to claim 9, wherein the shock absorber is used for an automobile bumper.

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