JP2013035949A - Polyolefin resin foamed particle and in-mold foam molding thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flame-retardant polyolefin resin foam molding excellent in in-mold moldability and surface appearance, further satisfying FMVSS flammability, even when small particle size carbon black that deteriorates flame retardancy is added, with an inexpensive formulation.SOLUTION: This polyolefin resin foamed particle is obtained by foaming a polyolefin resin particle including 0.1-5 pts.wt. of metal salt hydrate and 0.5-20 pts.wt. of carbon black based on 100 pts.wt. of a polyolefin resin.

Description

  TECHNICAL FIELD The present invention relates to a polyolefin resin expanded particle having improved flame retardancy and a flame retardant polyolefin resin expanded particle molded body obtained by fusing polyolefin expanded resin particles to each other.

  In-mold foam moldings obtained by filling polyolefin resin foam particles, in which polyolefin resin particles are foamed, into a mold for in-mold foam molding and then heat-sealing them, are already packaging materials, buffer It is used in a wide range of applications such as wood, heat insulation, building materials, and automotive parts.

  Among these uses, in the field of building materials and automobile parts, it is required to have flame retardancy, and a polypropylene system containing a flame retardant and a flame retardant aid in the resin as necessary. In-mold foam moldings using resin foam particles and polypropylene resin foam particles have been proposed (for example, Patent Documents 1 and 2).

  In addition, there are cases where polyolefin resin foam particles colored from the point of appearance and in-mold foam moldings using the polyolefin resin foam particles are required, especially in the field of automobile parts, the blackened polyolefin resin foam Since black particles and in-mold foam moldings are required, carbon black is generally used for in-mold foam moldings from the viewpoint of coloring power, heat resistance, and the like. On the other hand, in recent years, these materials have been reduced in weight, and there is an increasing demand for a material having a high foamed molded article.

  Automobile interior members and the like often have to meet flammability standards, and materials that are flame retardant or have a low burning rate are required. However, in-mold foam moldings using carbon black and in-mold foam moldings with a high expansion ratio tend to burn easily, and black in-mold foam moldings with a high expansion ratio are difficult to meet flammability standards. There are many trends.

  Various methods for making flame-retardant polyolefin resins that are inherently flammable have been studied, and a method of adding a flame retardant is common. As flame retardants for polyolefin resins, various flame retardants such as halogen-containing compounds, hydrated metals, phosphate esters, nitrogen-containing compounds are used, and such flame retardants are used in polyolefin resin foams. As an example, Patent Literatures 1 to 4 are typically mentioned. In recent years, halogen-containing compounds are favored by non-halogen flame retardants due to environmental problems such as the possibility of generation of gases harmful to the human body during combustion, as well as hydration represented by magnesium hydroxide. Non-halogen flame retardants such as metals are often used in a large amount with respect to resins, which may cause deterioration of mechanical properties and moldability.

  In recent years, it has been proposed to use a sterically hindered amine ether-based flame retardant as a non-halogen flame retardant in a polypropylene resin-in-mold foam-molded product (see Patent Documents 5 to 6). However, when a sterically hindered amine ether flame retardant is used in a polypropylene resin-in-mold foam-molded product containing carbon black, the flame retardancy may not be sufficient. Such organic compound molecular flame retardants are very expensive, may have low heat resistance, and may limit processing conditions.

JP-A-7-309967 JP-A-10-147661 JP 7-258447 A JP-A-3-2877637 International Publication No. 2003/048239 JP 2004-263033 A

Although the flame retardant level required for the in-mold foam molded product varies depending on the application, the object of the present invention is to have in-mold moldability, surface appearance, etc. while having the white or black color preferred for automotive parts and the like. No flame retardant polyolefin resin foamed particles that can produce a flame retardant polyolefin resin in-mold foam molded body that is less flammable than conventional in-mold foam molded articles are provided by an inexpensive flame retardant formulation.
In particular, when carbon black is used for blackening polyolefin resin foam particles and in-mold foam moldings, it is known that black color can be improved by using carbon black with a fine particle size, On the other hand, flame retardancy tends to decrease, and it is necessary to use a large amount of expensive flame retardant.

  As a result of diligent research in view of the above problems, the present inventor has obtained a flame-retardant polyolefin-based resin that is less flammable than before by using polyolefin-based resin expanded particles containing a specific metal salt hydrate with respect to a polyolefin-based resin. It has been found that an in-mold foam molded product can be obtained with an inexpensive formulation.

That is,
The first of the present invention is to foam polyolefin resin particles containing 0.1 to 10 parts by weight of metal salt hydrate and 0.5 to 20 parts by weight of carbon black with respect to 100 parts by weight of polyolefin resin. It is related with the polyolefin-type resin expanded particle characterized by being obtained.

As a preferred embodiment,
(1) Metal salt hydrate is calcium sulfate dihydrate, calcium sulfate 1/2 hydrate, magnesium sulfate trihydrate, magnesium sulfate heptahydrate, aluminum sulfate octahydrate, trisodium phosphate Is at least one selected from the group consisting of 12 hydrates,
(2) The particle size of carbon black in the polyolefin resin expanded particles is 30 to 100 nm.
(3) As other flame retardants, 0.01 to 0.2 parts by weight of a sterically hindered amine ether flame retardant is included,
(4) The polyolefin resin is polypropylene,
The present invention relates to the polyolefin resin expanded particles described above.

  A second aspect of the present invention relates to an in-mold foam molded article comprising the above-described carbon black-containing polyolefin resin foam particles.

  The in-mold foam molded article comprising the polyolefin resin expanded particles of the present invention has good flame retardancy even when a small amount of use is not used in the FMVSS302 combustion test method, or even when a small amount is used. The appearance is also free of uneven color and wrinkles.

It is an example of a DSC curve obtained when the polyolefin resin expanded particles of the present invention are heated at a rate of 10 ° C./min from 40 ° C. to 220 ° C. with a differential scanning calorimeter (DSC). The low-temperature side melting peak, the low-temperature side melting peak calorie, which is the amount of heat enclosed by the tangent to the melting start baseline from the maximum point between the low-temperature side peak and the high-temperature side peak, is Ql, and the high-temperature side melting peak of the DSC curve Qh is the high-temperature side melting peak calorie, which is the amount of heat surrounded by the tangent line from the local maximum point between the low-temperature side peak and the high-temperature side peak to the melting end baseline.

  The polyolefin resin expanded particles of the present invention comprise polyolefin resin particles containing 0.1 to 10 parts by weight of metal salt hydrate and 0.5 to 20 parts by weight of carbon black with respect to 100 parts by weight of polyolefin resin. By obtaining it by foaming, an in-mold foam molded article that exhibits good flame retardancy in the FMVSS 302 combustion test method and excellent in appearance can be obtained.

  The polyolefin resin used in the present invention is a polymer comprising 75% by weight or more and 100% by weight of an olefin monomer, and preferably comprises 80% by weight or more and 100% by weight or less of an olefin monomer. It is a polymer. The polyolefin resin used in the present invention may contain 25% by weight or less, preferably 20% by weight or less, of other monomers copolymerizable with the olefin monomer.

  Specific examples of the olefin monomer include, for example, ethylene, propylene, butene-1, isobutene, pentene-1, 3-methyl-butene-1, hexene-1, 4-methyl-pentene-1, 3, 4 Examples thereof include α-olefins having 2 to 12 carbon atoms such as dimethyl-butene-1, heptene-1, 3-methyl-hexene-1, octene-1, and decene-1. These may be used alone or in combination of two or more.

  Specific examples of other monomers copolymerizable with the olefin monomer include, for example, cyclopentene, norbornene, 1,4,5,8-dimethano-1,2,3,4,4a, 8. , 8a, 6-octahydronaphthalene and other cyclic olefins, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6 -Diene such as octadiene. These may be used alone or in combination of two or more.

  Specific examples of the olefin resin include, for example, polyethylene resins mainly composed of ethylene such as high density polyethylene, medium density polyethylene, low density polyethylene, and linear low density polyethylene, and polypropylene based mainly on propylene. Resin. These polyolefin resins may be used alone or in combination of two or more. Among these, as the polyolefin resin, it is preferable to use a polypropylene resin from the viewpoint that it is easy to obtain expanded particles having an expansion ratio from low to high, and that the strength in the case of forming an in-mold product is high.

  The polypropylene resin is not particularly limited as long as it contains propylene as a main component of the monomer. For example, propylene homopolymer, α-olefin-propylene random copolymer, α-olefin-propylene block copolymer Etc. These may be used alone or in combination of two or more. Among these, a polypropylene resin containing ethylene as a comonomer component, in which the α-olefin is ethylene, is particularly preferable because it can be molded in a mold with a low vapor pressure.

In the polypropylene resin, the preferable ethylene content is 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight, further 3.5% by weight to 6% by weight, particularly 3.5% by weight or more. 5% by weight or less.
In addition, the ethylene content of the comonomer component in the polypropylene resin can be measured using 13C-NMR.

The melting point of the polypropylene resin used in the present invention is preferably 130 ° C. or higher and 165 ° C. or lower, more preferably 135 ° C. or higher and 155 ° C. or lower.
When the melting point of the polypropylene resin is less than 130 ° C., the heat resistance and mechanical strength tend to be insufficient. In addition, when the melting point of the polypropylene resin exceeds 165 ° C., it tends to be difficult to ensure the fusion at the time of the bead method in-mold foam molding.
Here, the melting point of the polypropylene resin is 1-10 mg of the polypropylene resin at a rate of 10 ° C./min from 40 ° C. to 220 ° C. using a differential scanning calorimeter, and then 10 ° C./min to 40 ° C. Is the peak temperature of the endothermic peak in the DSC curve obtained when the temperature is increased to 220 ° C. at a rate of 10 ° C./min.

The melt flow rate (hereinafter referred to as “MFR”) of the polypropylene resin used in the present invention is preferably 0.5 g / 10 min or more and 30 g / 10 min or less, more preferably 2 g / 10 min or more and 20 g / min. The thing of 10 minutes or less is preferable.
When the MFR of the polypropylene resin is less than 0.5 g / 10 min, it may be difficult to obtain a high expansion ratio polypropylene resin pre-expanded particle, and when it exceeds 30 g / 10 min, the foam of the polypropylene resin pre-expanded particle Tends to break, and the open cell ratio of the polypropylene resin pre-expanded particles tends to increase.
Here, the MFR of the polypropylene resin is measured at a temperature of 230 ° C. and a load of 2.16 kg in accordance with JIS K7210.

  The ratio (Mw / Mn) of the weight average molecular weight (hereinafter sometimes referred to as Mw) and the number average molecular weight (hereinafter sometimes referred to as Mn) of the polypropylene resin used in the present invention is not particularly limited. 3.0 or more, and particularly preferably 3.0 or more and 6.0 or less.

Here, Mn and Mw are measured under the following conditions.
Measuring instrument: Alliance GPC 2000 type gel permeation chromatography (GPC) manufactured by Waters
Column: 2 TSKgel GMH6-HT,
Two TSKgel GMH6-HTL (each inner diameter 7.5mm x length 300mm, manufactured by Tosoh Corporation)
Mobile phase: o-dichlorobenzene (containing 0.025% BHT)
Column temperature: 140 ° C
Flow rate: 1.0 mL / min
Sample concentration: 0.15% (W / V) -o-dichlorobenzene injection amount: 500 μL
Molecular weight calibration: Polystyrene conversion (calibration with standard polystyrene)

Examples of the polyethylene resin used in the present invention include ethylene homopolymer, ethylene-α-olefin random copolymer, ethylene-α-olefin block copolymer, low density polyethylene, high density polyethylene, and linear low density polyethylene. Is mentioned.
Here, as an alpha olefin, a C3-C15 alpha olefin etc. are mentioned, These may be used independently and may be used together 2 or more types.

  Among these polyethylene-based resins, good foamability when ethylene-α-olefin block copolymer has a comonomer content other than ethylene of 1 to 10% by weight or is a linear low density polyethylene And can be suitably used.

  The melting point of the polyethylene resin used in the present invention is preferably 110 ° C. or more and 140 ° C. or less, and further 120 ° C. or more and 130 ° C. or less is excellent in foamability and moldability, and within the polyolefin resin mold. Since it tends to be able to obtain pre-expanded particles having excellent mechanical strength and heat resistance when formed into a foamed molded product, it is more preferable.

The MFR of the polyethylene resin used in the present invention is preferably 0.5 g / 10 min or more and 30 g / 10 min or less, more preferably 1 g / 10 min or more and 5 g / 10 min or less, and 1.5 g It is particularly preferable that it is / 10 minutes or more and 2.5 g / 10 minutes or less.
When the MFR of the polyethylene resin is less than 0.5 g / 10 minutes, it becomes difficult to obtain pre-expanded particles having a high expansion ratio, and the bubbles tend to be non-uniform. Further, when the MFR of the polyethylene resin exceeds 30 g / 10 minutes, although it is easy to foam, the bubbles are liable to be broken, the open-cell ratio of the pre-foamed particles tends to be high, and the bubbles are also non-uniform. Tend.
Here, the MFR of the polyethylene resin is a value measured at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210.

  The polyolefin-based resin used in the present invention may be used by mixing a plurality of types of polyolefin-based resins, if necessary, or other thermoplastic resins that can be used by mixing with polyolefin-based resins, for example, Polystyrene, ionomer, etc. may be used in combination as long as the properties of the polyolefin resin are not lost.

  The polyolefin-based resin may be used by mixing a plurality of types of polyolefin-based resins as necessary, or other thermoplastic resins that can be used by mixing with polyolefin-based resins (for example, polystyrene, ionomer, etc.) ) May be used in combination as long as the properties of the polyolefin resin are not lost.

The polyolefin resin used in the present invention can be obtained by using a catalyst such as a Ziegler catalyst, a metallocene catalyst, a post metallocene catalyst.
When a Ziegler catalyst is used, a polymer having a large Mw / Mn tends to be obtained.

  Moreover, when the polymer obtained using these catalysts is oxidized and decomposed with an organic peroxide, characteristics such as molecular weight and MFR can be adjusted.

  Examples of the organic peroxide used in the present invention include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butylperoxylaurate, 2,5-dimethyl2, Examples include 5-di (benzoylperoxy) hexane, t-butylperoxybenzoate, dicumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, and t-butylperoxyisopropyl monocarbonate.

  When the organic peroxide is used, the amount of the organic peroxide used is preferably 0.001 part by weight or more and 0.1 part by weight or less with respect to 100 parts by weight of the polyolefin resin. In order to oxidatively decompose the polyolefin resin, for example, a polyolefin resin to which an organic peroxide is added can be heated and melted in an extruder.

  The polyolefin resin used in the present invention is preferably in a non-crosslinked state, but may be crosslinked by treatment with an organic peroxide or radiation.

  In the present invention, by containing 0.1 to 10 parts by weight of a metal salt hydrate with respect to 100 parts by weight of the polyolefin-based resin, self-extinguishing property and retardability at the time of combustion in the mold can be improved. it can.

  Examples of the metal salt hydrate used in the present invention include calcium sulfate dihydrate, calcium sulfate 1/2 hydrate, magnesium sulfate trihydrate, magnesium sulfate heptahydrate, and aluminum sulfate octahydrate. , Trisodium phosphate 12 hydrate, and the like are available, and can be obtained at a relatively low cost, and flame retardancy can be obtained at low cost.

  As physical properties of these metal salt hydrates, the DSC curve measured by a differential scanning calorimeter has an endothermic peak between 70 and 200 ° C., and the flame retardancy can be improved by endotherm at a low temperature. It can be done.

The content of the metal salt hydrate in the polyolefin resin particles of the present invention is preferably 0.1 to 5 parts by weight, and 0.3 to 3 parts by weight with respect to 100 parts by weight of the polyolefin resin. It is more preferable that
If the content of the metal salt hydrate is less than 0.1 parts by weight, the flame retardant effect may not be sufficient, and if it exceeds 5 parts by weight, the surface properties of the resulting foam tend to deteriorate.

  The metal salt hydrate used in the present invention may be pulverized using an airflow pulverizer, a mechanical pulverizer or the like before being added to the polyolefin resin.

  In the polyolefin resin expanded particles of the present invention, carbon black is contained in the polyolefin resin particles in order to obtain a black molded body.

  Specific examples of the carbon black used in the present invention include, for example, channel black, roller black, disc, gas furnace black, oil furnace black, thermal black, acetylene black and the like. These may be used alone or in combination of two or more.

The content of carbon black in the polyolefin resin particles in the present invention is preferably 0.5 parts by weight or more and 20 parts by weight or less, with respect to 100 parts by weight of the polypropylene resin particles. It is more preferable that the amount is not more than parts.
When the content of carbon black is less than 0.5 parts by weight, it tends to be difficult to blacken sufficiently, and when it exceeds 20 parts by weight, the cell diameter of the obtained polypropylene resin expanded particles tends to be finer. Thus, not only the in-mold foam moldability (particularly the surface appearance) tends to deteriorate, but also there is a tendency that sufficient flame retardancy cannot be obtained.

  In the present invention, when preparing resin particles containing carbon black, the carbon black is a polyolefin resin obtained by dispersing carbon black (hereinafter referred to as “carbon black masterbatch”). It is preferable to melt and knead together.

Examples of the polyolefin resin used in the carbon black masterbatch include a polyethylene resin and a polypropylene resin.
Examples of the polypropylene resin include the above-mentioned resins, but it is preferable to use a polypropylene resin having an MFR of 10 g / 10 min or more because a masterbatch can be easily produced.

The carbon black concentration in the carbon black masterbatch is preferably 5% by weight to 60% by weight, and more preferably 20% by weight to 50% by weight.
A stabilizer or a lubricant may be added to the carbon black masterbatch.

  The carbon black masterbatch can be produced by melt-kneading a polyolefin resin and carbon black using an extruder, kneader, Banbury mixer, roll, or the like. It is particularly preferable to use an extruder.

  The carbon black in the carbon masterbatch improves the blackness when it is dispersed in the resin as much as possible. Therefore, when carbon black is used as a colorant, it is necessary to adjust the aggregates and aggregates to be small. It is normal.

The average primary particle diameter of carbon black in the polyolefin resin expanded particles of the present invention is preferably 10 nm to 200 nm, and more preferably 30 nm to 100 nm.
By incorporating the sterically hindered amine ether flame retardant into the polyolefin resin expanded particles of the present invention, the target flame retardancy can be obtained with a small amount of flame retardant added.

  Preferable examples of the sterically hindered amine ether flame retardant include, for example, the general formula (1):

Wherein R 1 and R 2 are the general formula (2):

(In the formula, R ⁵ is methyl group, ethyl group, propyl group, butyl group, n-pentyl group, n-hexyl group, n-heptyl group, nonyl group, decyl group, undecyl group, dodecyl group, isopropyl group, Isobutyl group, second butyl group, third butyl group, 2-ethylbutyl group, isopentyl group, 1-methylpentyl group, 1,3-dimethylbutyl group, 1-methylhexyl group, isoheptyl group, 1,1,3, An alkyl group having 1 to 12 carbon atoms such as 3-tetramethylpentyl group, 1-methylundecyl group, 1,1,3,3,5,5-hexamethylhexyl group, R ⁶ is a methyl group, groups represented by a cyclohexyl group or an octyl group), R ³ and a group one of R ⁴ is represented by the general formula (2), compounds represented by the other of R ³ and R ⁴ represents a hydrogen atom) And the like.
The sterically hindered amine ether flame retardant may be used alone or in combination of two or more.

  Specific examples of the group represented by the general formula (2) include, for example, 2,4-bis [(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino]. -S-triazine, 2,4-bis [(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine, 2,4-bis [( 1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine and the like.

  Specific examples of the sterically hindered amine ether flame retardant represented by the general formula (1) include, for example, N, N ′, N ′ ″-tris {2,4-bis [(1-cyclohexyloxy-2 , 2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazin-6-yl} -3,3′-ethylenediiminopropylamine; N, N ′, N ″ — Tris {2,4-bis [(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine-6yl} -3,3′-ethylene Diiminodipropylamine; N, N ′, N ′ ″-tris {2,4-bis [(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino ] -S-triazine-6yl} -3 3′-ethylenediiminodipropylamine; N, N ′, N ″ -tris {2,4-bis [(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) n -Butylamino] -s-triazin-6yl} -3,3′-ethylenediiminopropylamine; N, N ′, N ′ ″-tris {2,4-bis [(1-methoxy-2,2 , 6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine-6yl} -3,3′-ethylenediiminopropylamine; N, N ′, N ″ -tris {2 , 4-Bis [(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylamino] -s-triazine-6yl} -3,3′-ethylenediiminopropylamine Etc. These may be used alone or in combination of two or more.

The blending ratio of the sterically hindered amine ether flame retardant to the polyolefin resin in the present invention is 0.01 parts by weight or more and 0.2 parts by weight of the sterically hindered amine ether flame retardant with respect to 100 parts by weight of the polyolefin resin particles. The amount is preferably not more than parts by weight, more preferably not less than 0.02 parts by weight and not more than 0.1 parts by weight.
When the blending ratio of the sterically hindered amine ether flame retardant is less than 0.01 parts by weight, sufficient flame retardancy tends to be difficult to obtain, and when it exceeds 0.2 parts by weight, the cost increases. Tends to be economically disadvantageous.

  The present invention may further contain a benzotriazole-based ultraviolet absorber, a hindered amine-based light stabilizer, a phenol-based antioxidant, a phosphite-based processing stabilizer, a sulfur-based heat stabilizer, and the like.

  The benzotriazole-based UV absorber is not particularly limited as long as it can be generally used for a resin, but preferred specific examples include 2- (2-hydroxy-3-tert-butyl-5-methylphenyl). -5-chlorobenzotriazole, 2- (2-hydroxy-5-methylphenyl) -benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) -5-chlorobenzo And triazol, 2- (2-hydroxy-3,5-di-t-amylphenyl) -benzotriazole, 2- (2-hydroxy-5-t-octylphenyl) -benzotriazole and the like. These may be used alone or in combination of two or more. Among these, 2- (2-hydroxy-3-t-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-5-methylphenyl) -benzotriazole, 2 -(2-Hydroxy-3,5-di-t-butylphenyl) -5-chlorobenzotriazole is preferred.

The amount of the benzotriazole ultraviolet absorber used is preferably 0.01 parts by weight or more and 1.0 parts by weight or less, more preferably 0.1 parts by weight or more and 0.5 parts by weight or less with respect to 100 parts by weight of the polyolefin resin. It is more preferable that the amount is not more than parts by weight.
When the amount of the benzotriazole ultraviolet absorber used is less than 0.01 parts by weight, it may be difficult to obtain a sufficient flame retardant improvement effect, and when it exceeds 1.0 parts by weight, the cost increases. May be economically disadvantageous.

  The hindered amine light stabilizer is not particularly limited as long as it can generally be used for a resin, but preferred specific examples include bis (2,2,6,6-tetramethyl-4-piperidyl) separate, Bis (1,2,2,6,6-pentamethyl-4-piperidyl) separate, poly [[6-[(1,1,3,3-tetramethylbutyl) amino] -1,3,5-triazine- 2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidyl) imino]] and the like, and these may be used alone or in combination of two or more. . Among these, bis (2,2,6,6-tetramethyl-4-piperidyl) separate is preferable.

The amount of the hindered amine light stabilizer used is preferably 0.01 parts by weight or more and 1.0 parts by weight or less, and 0.1 parts by weight or more and 0.5 parts by weight or less with respect to 100 parts by weight of the polyolefin resin. It is more preferable that
When the amount of the hindered amine light stabilizer used is less than 0.01 parts by weight, it may be difficult to obtain a sufficient flame retardant improvement effect, and when it exceeds 1.0 parts by weight, the cost increases. May be economically disadvantageous.

  The phenolic antioxidant is not particularly limited as long as it can be used for the resin, and preferred specific examples include tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl). Propionate] methane, tris (3,5-di-t-butyl-4 · hydroxybenzyl) isocyanurate, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 1 1,3-tris (2methyl-4hydroxy-5-t-butylphenyl) butane, and the like may be used alone or in combination of two or more. Among these, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, tris (3,5-di-t-butyl-4 · hydroxybenzyl) isocyanurate Is preferred. These may be used alone or in combination of two or more.

The amount of the phenolic antioxidant used is preferably 0.01 parts by weight or more and 1.0 parts by weight or less, and 0.1 parts by weight or more and 0.5 parts by weight or less with respect to 100 parts by weight of the polyolefin resin. It is more preferable that
If the amount of the phenolic antioxidant used is less than 0.01 parts by weight, it may be difficult to obtain a sufficient flame retardant improvement effect. If it exceeds 1.0 parts by weight, the cost increases. May be economically disadvantageous.

  The phosphite processing stabilizer is not particularly limited as long as it can be used for the resin. Preferred specific examples include tris (2,4-di-t-butylphenyl) phosphite and bis (2,4 -Di-t-butylphenyl) pentaerythritol diphosphite, tris (mono, dinonylphenyl) phosphite and the like may be mentioned, and these may be used alone or in combination of two or more. Among these, tris (2,4-di-t-butylphenyl) phosphite is preferable.

The amount of the phosphite processing stabilizer used is preferably 0.01 parts by weight or more and 1.0 parts by weight or less, and 0.1 parts by weight or more and 0.5 parts by weight or less with respect to 100 parts by weight of the polyolefin resin. The following is more preferable.
When the amount of the phosphite processing stabilizer used is less than 0.01 parts by weight, it may be difficult to obtain a sufficient flame retardant improvement effect, and when it exceeds 1.0 parts by weight, the cost increases. May be economically disadvantageous.

  The sulfur-based heat stabilizer is not particularly limited as long as it can be used for the resin, but preferred specific examples include distearyl thiodipropionate, dilauryl thiodipropionate, dimyristyl thiodipropionate, ditrileate. Decyl thiodipropionate etc. are mentioned, These may be used independently and may be used in combination of 2 or more type. Among these, distearyl thiodipropionate is preferable.

The amount of the sulfur heat stabilizer used is preferably 0.01 parts by weight or more and 1.0 parts by weight or less, and 0.1 parts by weight or more and 0.5 parts by weight or less with respect to 100 parts by weight of the polyolefin resin. It is more preferable that
When the blending ratio of the sulfur-based heat stabilizer is less than 0.01 parts by weight, it may be difficult to obtain a sufficient flame retardant improvement effect, and when it exceeds 1.0 parts by weight, the cost increases. May be economically disadvantageous.

  The flame retardancy in the present invention is determined based on a combustion test method defined in FMVSS 302 for a polyolefin resin-in-mold foam-molded product obtained using polyolefin resin foam particles. In the evaluation by the test method to be described later, it is preferably slow-flammability or self-extinguishing property, and more preferably self-extinguishing property.

The polyolefin resin particles used in the present invention include polyolefin resins, metal salt hydrates and carbon black master batches, and other additives such as sterically hindered amine ether flame retardants, extruders, kneaders, and banburys. After melt-kneading using a mixer, a roll, etc., it is obtained as polyolefin resin particles having a cylindrical shape, an elliptical shape, a spherical shape, a cubic shape, a rectangular parallelepiped shape or the like.
The phosphorus flame retardant and the sterically hindered amine ether flame retardant may also be melt-kneaded as a master batch dispersed in a polyolefin resin.

The polyolefin resin particles in the present invention preferably have a weight of 0.1 mg or more and 30 mg or less, more preferably 0.3 mg or more and 10 mg or less in order to obtain foam particles having an appropriate average maximum diameter. .
The weight of one polyolefin resin particle is the average resin particle weight of 100 particles randomly selected from the polyolefin resin particles.

  In the present invention, the polyolefin resin particles, if necessary, including cell nucleating agents such as talc, antioxidants, metal deactivators, phosphorus processing stabilizers, ultraviolet absorbers, ultraviolet stabilizers, fluorescent Whitening agents, stabilizers such as metal soaps or cross-linking agents, chain transfer agents, lubricants, plasticizers, fillers, reinforcing agents, other flame retardants, surfactant-type or polymer-type antistatic agents, conductivity improvement You may add an agent etc. in the range which does not impair the effect of this invention.

The polyolefin resin foamed particles of the present invention are obtained, for example, by dispersing the polyolefin resin particles in a dispersion medium in the presence of a foaming agent in a sealed container and heating to a temperature equal to or higher than the softening temperature of the polyolefin resin particles. It can be obtained by releasing the dispersion medium together with the dispersion medium in a low-pressure atmosphere.
The heating temperature in the sealed container is preferably the melting point of polyolefin resin particles −25 ° C. or higher and the melting point of polyolefin resin particles + 25 ° C. or lower, the melting point of polyolefin resin particles −15 ° C. or higher and the melting point of polyolefin resin particles + 15 ° C. or lower. A range of temperatures is more preferred. After heating and pressurizing to this temperature and impregnating the polyolefin resin particles with the foaming agent, one end of the sealed container is opened to release the polyolefin resin particles into a lower pressure atmosphere than in the sealed container. Thus, polyolefin resin expanded particles can be produced.

  There are no particular limitations on the sealed container in which the polyolefin resin particles are dispersed, and any container that can withstand the pressure and temperature in the container at the time of producing the polyolefin resin foam particles can be used. For example, an autoclave type container can be mentioned.

  As the dispersion medium, methanol, ethanol, ethylene glycol, glycerin, water, and the like can be used, and it is preferable to use water among them.

In order to prevent coalescence of the polyolefin resin particles in the dispersion medium, it is preferable to use a dispersant. Examples of the dispersant include inorganic dispersants such as tricalcium phosphate, magnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, and clay. Further, if necessary, for example, sodium dodecylbenzene sulfonate, sodium n-paraffin sulfonate, sodium α-olefin sulfonate, magnesium sulfate, magnesium nitrate, magnesium chloride, aluminum sulfate, aluminum nitrate, aluminum chloride, iron sulfate, nitric acid It is preferable to use a dispersion aid such as iron or iron chloride in combination.
Among these, combined use of tricalcium phosphate and sodium n-paraffin sulfonate is more preferable.

  The amount of dispersant and dispersion aid used varies depending on the type and type and amount of polyolefin resin used, but usually 0.2 parts by weight or more and 3 parts by weight or less of the dispersant with respect to 100 parts by weight of the dispersion medium. It is preferable to add 0.001 part by weight or more and 0.1 part by weight or less of a dispersion aid. The polyolefin resin particles are usually preferably used in an amount of 20 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the dispersion medium in order to improve the dispersibility in the dispersion medium.

  In producing polyolefin resin expanded particles, there is no particular limitation on the blowing agent. For example, aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane; inorganic gases such as air, nitrogen, and carbon dioxide; water Etc. and mixtures thereof can be used.

  When using water as a foaming agent, in order to obtain polyolefin resin foamed particles having a high foaming ratio, one or more compounds among hydrophilic polymer, polyhydric alcohol, and compounds having a triazine skeleton are added to the polyolefin resin particles. It is preferable to do. Here, the hydrophilic polymer is an ionomer obtained by crosslinking ethylene-acrylic acid-maleic anhydride terpolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid copolymer with metal ions. Examples thereof include carboxyl group-containing polymers such as resins, polyethylene glycol and the like. These may be used alone or in combination of two or more.

The amount of the hydrophilic polymer used varies depending on the type of the hydrophilic polymer and is not particularly limited, but is preferably 0.01 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the polyolefin resin particles. .1 to 5 parts by weight is more preferable.
When the amount of the hydrophilic polymer used is less than 0.01 part by weight, there is a tendency that polyolefin resin expanded particles having a high expansion ratio are difficult to obtain. When the amount exceeds 20 parts by weight, the heat resistance and mechanical strength are greatly reduced. There is.

  Examples of the polyhydric alcohol include ethylene glycol, glycerin, erythritol, and pentaerythritol. These may be used alone or in combination of two or more.

The compound having a triazine skeleton preferably has a molecular weight of 300 or less per unit triazine skeleton.
Here, the molecular weight per triazine skeleton is a value obtained by dividing the molecular weight by the number of triazine skeletons contained in one molecule. When the molecular weight per unit triazine skeleton exceeds 300, variation in expansion ratio and variation in cell diameter may be noticeable.

Examples of the compound having a molecular weight per unit triazine skeleton of 300 or less include melamine (chemical name 1,3,5-triazine-2,4,6-triamine), ammelin (1,3,5-triazine-2- Hydroxy-4,6-diamine), ammelide (1,3,5-triazine-2,4-hydroxy-6-amine), cyanuric acid (1,3,5-triazine-2,4,6-triol) ), Tris (methyl) cyanurate, tris (ethyl) cyanurate, tris (butyl) cyanurate, tris (2-hydroxyethyl) cyanurate, melamine isocyanuric acid condensate and the like. These may be used alone or in combination of two or more.
Among these, it is preferable to use melamine, isocyanuric acid, and a melamine / isocyanuric acid condensate in order to obtain high expansion ratio polyolefin-based resin expanded particles with small expansion ratio variation and cell diameter variation.

  In addition, when carbon dioxide is used as a foaming agent, a polyolefin-based resin having a high foaming ratio and a uniform cell diameter when a low molecular weight hydrophilic substance such as glycerin, polyethylene glycol having a molecular weight of 300 or less, or zinc borate is added to a polyolefin resin. There exists a tendency which can obtain the resin expanded particle.

  The expansion ratio of the polyolefin resin expanded particles obtained by the above production method is preferably 5 to 50 times, and more preferably 7 to 45 times.

Further, once the polyolefin resin expanded particles of 5 times to 35 times are manufactured, and the polyolefin resin expanded particles in the polyolefin resin expanded particles are subjected to pressure treatment in which the polyolefin resin expanded particles are put in a sealed container and impregnated with nitrogen, air, etc. After making the pressure higher than normal pressure, the polyolefin resin foamed particles having a higher expansion ratio may be obtained by a method such as a two-stage foaming method in which the polyolefin resin foamed particles are heated and further foamed with steam or the like.
Here, the expansion ratio is obtained by calculating the weight w (g) and the ethanol submerged volume v (cm ³ ) of the polyolefin resin foamed particles, and the density d (g / cm ³ ) of the polyolefin resin particles before foaming according to the following formula. It is what I have sought.
Foaming ratio = d × v / w

The polyolefin resin expanded particles of the present invention are obtained when the polyolefin resin expanded particles 5-6 mg are heated from 40 ° C. to 220 ° C. at a temperature increase rate of 10 ° C./min in the measurement by the differential scanning calorimetry method. It is preferable to have two melting peaks in the DSC curve.
Also, tangent lines are drawn to the DSC curve from the point where the endothermic amount becomes the smallest between the two melting peaks of the DSC curve, and the partial low temperature side surrounded by the tangent line and the DSC curve is defined as the melting peak heat amount Ql on the low temperature side, The ratio of the melting peak on the high temperature side (Qh / (Ql + Qh) × 100 (hereinafter abbreviated as “DSC ratio”)) calculated from these when the melting peak heat quantity Qh on the high temperature side is 13% or more It is preferably 50% or less, and more preferably 18% or more and 40% or less.
When the DSC ratio is within this range, a polyolefin resin-in-mold foam-molded article having a high surface beauty can be obtained.

When the polyolefin resin foamed particles of the present invention are used for in-mold foam molding,
B) Method to use as it is,
B) A method of previously injecting an inorganic gas such as air into the foamed particles to impart foaming ability;
C) Conventionally known methods such as a method of filling expanded particles in a mold in a compressed state and molding may be applied.

  As a specific method for in-mold foam molding of a polyolefin resin in-mold foam from the polyolefin resin foam particles of the present invention, for example, the polyolefin resin foam particles are pre-air-pressurized in a pressure resistant container, and the polyolefin resin foam The foaming ability is imparted by press-fitting air into the particles, and this is filled in a molding space that can be closed but cannot be sealed by two molds. Molding with heating steam pressure of about 4MPa for heating time of about 3 to 30 seconds, fusing polyolefin resin foamed particles together, and then cooling the mold by water cooling, then opening the mold, polyolefin resin mold Examples thereof include a method for obtaining an inner foam molded article.

The density of the polyolefin resin in-mold foam molded product obtained by using the polyolefin resin expanded particles of the present invention is preferably 10 kg / m ³ or more and 300 kg / m ³ or less, and 15 kg / m ³ or more and 250 kg / m ^3. Or less, more preferably 15 kg / m ³ or more and 25 kg / m ³ or less. In particular, when the density of the polyolefin resin-in-mold foam-molded product is 15 kg / m ³ or more and 25 kg / m ³ or less, the improvement in flame retardancy is remarkable.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited only to these Examples.

In the examples and comparative examples, the resins and compounds used are as follows.
● Polypropylene resin [ethylene-propylene random copolymer, ethylene content 2.1%, MFR = 7.1 g / 10 min, melting point 143 ° C.]
● Metal hydrate:
Calcium sulfate dihydrate [manufactured by Wako Pure Chemical Industries, Ltd., calcium sulfate dihydrate]
Magnesium sulfate trihydrate [manufactured by Umai Kasei Kogyo Co., Ltd., dried magnesium sulfate trihydrate]
Magnesium sulfate heptahydrate [manufactured by Umai Kasei Kogyo Co., Ltd., purified magnesium sulfate]
Trisodium phosphate 12 hydrate [manufactured by Taihei Chemical Industry Co., Ltd., trisodium phosphate]
Magnesium hydroxide [Albemarle, magnesium hydroxide]
● Carbon black:
Carbon blacks A and B were used as carbon black master batches containing 5% by weight of carbon blacks A and B in a polypropylene resin (MFR = 15 g / 10 min), respectively. In Table 1, the average particle diameter of carbon black in the obtained expanded particles is also shown.
● Sterically hindered amine ether flame retardant:
Ciba Specialty Chemicals, NOR116
The chemical formula is represented by the following chemical formula (3).

(Wherein R is the formula:

Represents a group represented by
● Nucleating agent:
Talc [Hayashi Kasei Co., Ltd., Talcan Powder PK-S]
● Hydrophilic polymer:
Polyethylene glycol [manufactured by Lion Corporation, PEG # 300]
Evaluation in Examples and Comparative Examples was performed as follows.

(Carbon black particle size)
The photograph which expanded the cross section of the cell membrane of the obtained polyolefin resin expanded particle 40,000 times with the transmission electron microscope was image | photographed. In the obtained transmission electron micrograph, the particle diameters (Ferre diameter) in the X direction and the Y direction of 50 carbon black particles were measured arbitrarily, and the average value was calculated as the carbon black particle diameter. .

(Flame retardance)
From the obtained foam, cut into a flame retardant test sample having a length of 350 mm, a width of 100 mm and a thickness of 12 mm, and a B mark at a position of 38 mm and a B mark at a position of 292 mm from one end in the length direction of the sample. Provided.
The flame retardancy evaluation was in accordance with the combustion test method defined in FMVSS302. Using a MVSS flammability tester (manufactured by Suga Test Instruments Co., Ltd.), a burner flame prepared at a height of 38 mm so that the end of the sample is the center of the flame is applied to the one end in the length direction of the sample for 15 seconds. The flame retardance was evaluated according to the following criteria from the state of combustion at that time.
A: Fire extinguished before the flame reaches the A mark or within 60 seconds or 50 mm after passing the A mark. It is said to have “self-extinguishing properties”.
○: When the flame burns beyond the A mark [38 mm from the sample edge where the flame hits] and reaches the B mark [292 mm from the sample edge where the flame hits],
Combustion rate exceeding A marked line, and after passing A marked line, the burning rate when extinguishing over 60 seconds or exceeding 50 mm is 100 mm / min or less. It is called “slow flammability”.
X: Neither self-extinguishing property nor retarding property is judged. It is called “flammability”.

(Blackness)
The surface of the obtained in-mold foam molding was visually observed and evaluated according to the following criteria.
A: High blackness.
○: Black.
Δ: Slightly thin
X: Thin.

(Foaming ratio)
The weight w (g) and the ethanol submerged volume v (cm ³ ) of the polyolefin resin expanded particles are obtained, and the density d (g / cm ³ ) of the polyolefin resin particles before foaming is obtained by the following formula.
Foaming ratio = d × v / w

(Average cell diameter)
30 foamed particles were arbitrarily taken out from the obtained polyolefin resin foamed particles, the cell diameter was measured in accordance with JIS K6402, and the average cell diameter was calculated.

(Closed cell rate)
By using an air comparison type hydrometer (BECKMAN, Model 930), the closed cell volume of the obtained foamed particles is obtained, and the closed cell volume is divided by the apparent volume obtained separately by the ethanol immersion method. The rate was calculated.

(DSC ratio)
5-6 mg of the obtained polyolefin resin expanded particles are heated from 40 ° C. to 220 ° C. at a temperature increase rate of 10 ° C./min using a differential scanning calorimeter [Seiko Instruments Co., Ltd., DSC6200R]. A DSC curve (illustrated in FIG. 1) obtained at that time was obtained.
The obtained DSC curve has two peaks, and was calculated from the melting peak calorie Ql on the low temperature side and the melting peak calorie Qh on the high temperature side of the melting peak by the following formula.
DSC ratio = Qh / (Ql + Qh) × 100

(Molded body density)
The volume v (liter) is obtained from the weight w (g), the length, the width, and the thickness of the sample for the combustion test in the (combustibility) evaluation, and is obtained by the following formula.
Compact density = w / v

(Surface appearance)
The surface of the obtained in-mold foam molding was visually observed and evaluated according to the following criteria.
○: There are no irregularities on the surface, and there is almost no gap between particles.
X: There are irregularities on the surface, and the gap between each particle is extremely large.

(Fusion rate)
The in-mold foam molded body is broken, its cross section is observed, the ratio of the number of broken particles to the total number of particles in the cross section is determined, and evaluated according to the following criteria.
○: The ratio of broken particles is 60% or more.
X: The ratio of broken particles is less than 60%.

(Examples 1-8)
[Preparation of polyolefin resin particles]
0.5 parts by weight of polyethylene glycol is pre-blended with 100 parts by weight of polypropylene resin, then 0.05 parts by weight of talc as a nucleating agent, calcium sulfate dihydrate as a flame retardant, magnesium sulfate 3 Hydrate, magnesium sulfate heptahydrate, trisodium phosphate dodecahydrate, sterically hindered amine ether, and carbon black A and carbon black B as colorants were added and mixed in the amounts shown in Table 1.
The resulting mixture was supplied to an extruder, melted and kneaded at a resin temperature of 210 ° C., then extruded from a cylindrical die (hole diameter 1.8 mm) installed at the tip of the extruder, cooled with water, cut with a cutter, Columnar polypropylene resin particles (1.2 mg / grain) were obtained.
[Production of polyolefin resin expanded particles]
After 100 parts by weight of the obtained polypropylene resin particles were put into a 200 liter sealed container together with 200 parts by weight of pure water, 0.6 part by weight of tricalcium phosphate and 0.04 part by weight of sodium n-paraffin sulfonate, While degassing and stirring, 7 parts by weight of carbon dioxide gas was placed in a sealed container and heated to 150 ° C. The pressure in the sealed container at this time was 2.9 MPa (gauge pressure). Immediately after opening the valve at the bottom of the sealed container, the aqueous dispersion (resin particles and aqueous dispersion medium) was discharged under atmospheric pressure through an orifice having a diameter of 3.5 mm to obtain expanded particles. At this time, during discharge, the pressure was maintained with carbon dioxide gas so that the pressure in the container did not decrease.
The obtained expanded particles were evaluated for expansion ratio, average cell diameter, closed cell ratio, and DSC ratio. The results are shown in Table 1.
[Fabrication of polyolefin-based in-mold molded products]
The obtained foamed particles are filled with a mold having a length of 400 mm, a width of 300 mm, and a thickness of 12 mm with polypropylene resin foam particles in which an internal pressure of 0.18 to 0.23 MPa is applied by air pressurization in a pressure vessel. The foamed particles were heated and fused with water vapor of 0.28 MPa (gauge pressure) for 10 seconds to obtain a foamed molded product in a polypropylene resin mold.
With respect to the obtained in-mold foamed molded product, the molded product density, surface appearance, fusion rate, flame retardancy and blackness were evaluated. The results are shown in Table 1.

(Comparative Examples 1-7)
In [Production of polyolefin resin particles], the polyolefin resin foamed particles and the polyolefin were the same as in the examples except that the type and amount of the flame retardant and the type and amount of the colorant were changed as shown in Table 2. An in-mold foam was obtained.
Table 2 shows the evaluation results of the obtained foamed particles and the in-mold foam molded article.

The molded bodies obtained by changing the metal salt hydrates in Examples 1 to 4 had high blackness, few surface grains, good surface appearance, and good fusion. As a result of the FMVSS combustion test, it exhibited a slow flame retardancy and a self-extinguishing property, and was a good molded article in comprehensive evaluation. On the other hand, when the metal salt hydrates of Comparative Examples 1 and 2 were changed to 0.05 parts by weight and a very small amount of addition, the burning rate was 100 mm / min or more, and the burning rate was rejected.
Moreover, in Example 5, when carbon black A was increased to 6 weight part, the blackness was very favorable and the flame retardance was also satisfied. In Comparative Example 3, when carbon black A was added in a large amount of 22 parts by weight, the combustion rate was rejected.
When the flame retardant formulation using the metal salt hydrate of Example 6 and the sterically hindered amine ether was used in combination, the flame retardancy, surface properties, blackness, and fusion were good.

In Examples 7 and 8, the carbon black B was changed to use a metal salt hydrate, and the self-extinguishing property was better than that in Example 5. The larger the particle size of the carbon black, the better the flame retardancy, although the blackness is slightly lowered.
In Comparative Example 4, when the metal salt hydrate was added in a large amount of 6 parts by weight, the surface appearance and fusion of the molded article were poor.
Comparative Examples 5 and 6 are cases where the amount of carbon black is different from that of Comparative Examples 1 and 2, but with a metal salt hydrate added in an extremely small amount of 0.05 parts by weight, the burning rate is 100 mm / min. As a result, the combustion rate was rejected.
In Comparative Example 7, 5 parts by weight of magnesium hydroxide was used, but the flame retardancy was unacceptable, and the cell diameter became fine, so the surface properties were poor and the blackness was low.

Claims (6)

  It is obtained by foaming polyolefin resin particles containing 0.1 to 10 parts by weight of metal salt hydrate and 0.5 to 20 parts by weight of carbon black with respect to 100 parts by weight of polyolefin resin. Polyolefin resin foam particles.   Metal salt hydrate is calcium sulfate dihydrate, calcium sulfate 1/2 hydrate, magnesium sulfate trihydrate, magnesium sulfate heptahydrate, aluminum sulfate octahydrate, trisodium phosphate 12 hydrate The polyolefin resin expanded particles according to claim 1, wherein the polyolefin resin expanded particles are at least one selected from the group consisting of products.   The polyolefin resin expanded particles according to claim 1 or 2, wherein the particle size of carbon black in the polyolefin resin expanded particles is 30 to 100 nm.   The polyolefin resin expanded particles according to any one of claims 1 to 3, comprising 0.01 to 0.2 parts by weight of a sterically hindered amine ether flame retardant as the other flame retardant.   The polyolefin resin expanded particle according to any one of claims 1 to 4, wherein the polyolefin resin is polypropylene. An in-mold foam-molded article obtained by foam-molding the polyolefin-based resin foam particles according to any one of claims 1 to 5.

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