Polyolefin resin foamed particles and polyolefin resin foamed molded articles

Abstract

The present invention relates to a polyolefin resin foamed particle and a polyolefin resin foamed molded body thereof. The polyolefin resin foamed particle of the present invention comprises a polyolefin resin, an inorganic hypophosphite and a melamine flame retardant, wherein the content of the inorganic hypophosphite is 1.6 to 10.0 parts by weight relative to 100 parts by weight of the polyolefin resin, and the content of the melamine flame retardant is 0.01 to 2.0 parts by weight. The present invention can further improve the flame retardant safety of the foamed product on the basis of ensuring that the foamed product has good moldability, while improving its oxygen index and flame retardant grade, and can reduce the generation of harmful gases during combustion.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer foaming materials, and specifically relates to polyolefin resin foaming particles, a polyolefin resin foaming molded body obtained by in-mold molding the polyolefin resin foaming particles, and uses thereof. Background Art

[0002] The polyolefin resin foamed particles obtained by foaming the polyolefin resin particles are filled into the mold for in-mold foaming and then heated and fused to form an in-mold foamed body. The in-mold foamed body has the characteristics of arbitrary shape, light weight, and thermal insulation. Moreover, compared with the polystyrene resin in-mold foamed body obtained by using polystyrene resin foamed particles, the polyolefin resin in-mold foamed body has better chemical resistance, heat resistance, and deformation recovery rate after compression. For this reason, polyolefin resin in-mold foamed bodies are often used in various applications such as cushioning materials, turnover boxes, thermal insulation materials, and automotive parts.

[0003] However, although the polyolefin resin in-mold foam molding has the above-mentioned excellent characteristics, it also has the disadvantage of being easy to burn. In particular, the foam molding has the disadvantages of high flammability and easy to burn compared with the non-foam molding. In recent years, it is expected that automotive parts, building materials and electrical and electronic product components have flame retardancy and self-fire extinguishing properties. In order to respond to these expectations, there are many studies on improving the flame retardancy of foam moldings. Generally, the method of adding flame retardants is adopted, such as using various flame retardants such as halogen-containing compounds, water and metal oxides, phosphates, nitrogen-containing compounds as flame retardants for polyolefin resins.

[0004] Patent Document 1 describes in an example an in-mold foamed product: by adding a sterically hindered amine ether type flame retardant as a non-halogen flame retardant to polyolefin resin pre-foamed particles, problems such as reduced in-mold foaming properties will not occur, and the product is suitable for HF-1 in the UL94 foam level test.

[0005] Patent Document 2 also describes an in-mold foamed molded product that uses the flame retardant and exhibits self-flammability in a combustion test based on FMVSS302, and the molded product also has a desired black tone.

[0006] Patent Document 3 describes flame-retardant polyolefin resin pre-expanded particles containing a halogen-containing pentavalent phosphate compound.

[0007] Patent Document 4 discloses that a polyolefin resin composition to which a sterically hindered amine ether flame retardant and a halogen-free phosphate ester are added is used to prepare polyolefin resin pre-expanded particles, thereby having good in-mold foaming properties and exhibiting flame retardancy superior to that of conventional particles.

[0008] Patent Document 5 selects a specific phosphorus-based flame retardant and can exhibit good flame retardancy under the FMVSS302 combustion test even if no sterically hindered amine ether compound is used or a small amount is used.

[0009] Patent Document 6 discloses polyolefin resin pre-expanded particles in which a hindered amine and an organic phosphorus compound are mixed at a specific weight ratio.

[0010] In addition, there are also many studies on improving the flame retardancy of non-foamed polyolefin materials. For example, patent document 7 discloses taking a certain amount of polypropylene, hypophosphite, melamine hydrobromide, flame retardant synergist, etc., pouring them into a high-speed mixer and stirring them evenly, then extruding and granulating them in a twin-screw extruder, and finally injecting them in an injection molding machine to obtain a high-efficiency flame retardant polyolefin composition, which can pass the UL94V-2 test. However, the situation of achieving flame retardancy in polyolefin foaming materials is more difficult than the situation of achieving flame retardancy in other forms of polyolefin films, tubes or non-foaming materials. The method suitable for non-foamed polyolefin materials may not be suitable for the foaming form corresponding to the polymer. In the manufacturing process of polyolefin resin foamed particles and their in-mold foaming moldings, including the impregnation of foaming agents, heating, rapid pressure release, and heating with steam, there are concerns about the decomposition of flame retardants or reactions caused by the mixing of flame retardants. Moreover, the moldability of the foaming material is likely to be affected by the presence of further additives, so that the final product may not meet the requirements of foamed products in the relevant fields of the industry.

[0011] Reference List

[0012] Patent Document 1: WO2003 / 048239A1

[0013] Patent Document 2: Japanese Patent Application Publication No. 2004-263033

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 9-227711

[0015] Patent Document 4: WO2010 / 119670A1

[0016] Patent Document 5: WO2013 / 022049A1

[0017] Patent Document 6: WO2016 / 052739A1

[0018] Patent document 7: CN105694221A Summary of the invention

[0019] Problem that the invention aims to solve

[0020] The flame retardant level required for the in-mold foaming molding varies with its use. The in-mold foaming molding prepared by the polyolefin resin foaming particles mentioned in the above-mentioned document can be appropriately used in various fields such as transportation, buildings, structures, furniture, electrical equipment and electronic equipment that require flame retardancy or self-extinguishing. However, in these fields and other fields such as the field of public transportation, the requirements for flame retardancy are becoming increasingly stringent. Therefore, there is a demand for further improving the flame retardancy of polyolefin foam materials. For example, in recent years, high-speed public transportation has been rapidly developed, and its development is not only a process of increasing speed, but also a process of continuously improving comfort and continuously strengthening reliability to meet the needs of social and economic development. As public transportation, high-speed transportation vehicles such as high-speed railways and airplanes have the characteristics of fast speed, large and dense flow of people. For the interior materials used therein, such as seat cores, etc., more stringent performance requirements such as fire retardancy, low smoke and low toxicity must be met than most other industries, such as higher flame retardant grades and higher oxygen indexes, etc., to ensure the safety of passengers' lives, because once a fire occurs in such transportation vehicles, huge casualties and property losses will be caused. The oxygen index refers to the oxygen concentration required for a material to reach its ignition point. The UL94 flame retardancy rating is used to evaluate the material's ability to extinguish after being ignited. These are two different methods of judging the flame retardancy of a material. Sometimes, although some materials have a high oxygen index, the UL94 test cannot reach a high level.

[0021] In order to solve the above technical problems, the present invention provides a polyolefin resin foamed particle and a polyolefin resin foamed molded body obtained by in-mold molding of the polyolefin resin foamed particle, which further improves the flame retardant safety of the foamed product while ensuring good moldability. Specifically, the oxygen index and UL94 flame retardant grade are improved at the same time, and the generation of harmful gases can be reduced during combustion.

[0022] Another object of the present invention is to provide an interior material for public transportation based on the polyolefin-based resin foam molded article.

[0023] Solutions for solving problems

[0024] The present invention includes the following technical solutions:

[0025] [1] A polyolefin resin foam particle, comprising a polyolefin resin, an inorganic hypophosphite and a melamine flame retardant, wherein the content of the inorganic hypophosphite is 1.6 to 10.0 parts by weight, and the content of the melamine flame retardant is 0.01 to 2.0 parts by weight, relative to 100 parts by weight of the polyolefin resin.

[0026] [2] The polyolefin resin foamed particles according to [1], wherein

[0027] The content of the inorganic hypophosphite is 1.8 to 4.0 parts by weight relative to 100 parts by weight of the polyolefin resin.

[0028] [3] The polyolefin resin foamed particles according to [1] or [2], wherein

[0029] The content of the melamine flame retardant is 0.01 to 0.3 parts by weight relative to 100 parts by weight of the polyolefin resin.

[0030] [4] The polyolefin resin foamed particles according to any one of [1] to [3], wherein the polyolefin resin foamed particles further include a compound represented by the general formula (1),

[0031] R 1 NHCH2CH2CH2NR 2 CH2CH2NR 3 CH2CH2CH2NHR 4 (1)

[0032] In the general formula (1), R 1 , R 2 is a group represented by the general formula (2), the dotted line above the triazine ring represented by the general formula (2) represents the connection portion with the nitrogen atom in the general formula (1), R 3 and R 4 One of them is a group represented by the general formula (2), the dotted line above the triazine ring represented by the general formula (2) represents the connection part with the nitrogen atom in the general formula (1), R 3 and R 4 The other side is a hydrogen atom. In the general formula (2), R 5 is an alkyl group having 1 to 12 carbon atoms, R 6 is methyl, cyclohexyl or octyl,

[0033]

[0034] [5] The polyolefin resin foamed particles according to [4], wherein

[0035] The content of the compound represented by the general formula (1) is 0.01 to 2.0 parts by weight relative to 100 parts by weight of the polyolefin resin.

[0036] [6] The polyolefin resin foam particles according to any one of the technical solutions [1] to [5], wherein the polyolefin resin particles also include one or more brominated flame retardants selected from the group consisting of brominated bisphenol A flame retardants, brominated bisphenol S flame retardants, brominated butadiene-styrene block copolymer flame retardants, and brominated polyphenylene ether flame retardants.

[0037] [7] The polyolefin resin foamed particles according to [6], wherein

[0038] The content of the brominated flame retardant is 0.1 to 5.0 parts by weight relative to 100 parts by weight of the polyolefin resin.

[0039] [8] The polyolefin resin foamed particles according to [6] or [7], wherein

[0040] The brominated flame retardant includes at least one of brominated bisphenol A flame retardant and brominated bisphenol S flame retardant.

[0041] [9] The polyolefin resin foamed particles according to any one of [1] to [8], wherein the polyolefin resin foamed particles further include a free radical initiator.

[0042]

[10] The polyolefin resin foamed particles according to [9], wherein the content of the radical initiator is 0.01 to 0.2 parts by weight based on 100 parts by weight of the polyolefin resin.

[0043]

[11] The polyolefin resin foamed particles according to [9] or

[10] , wherein the radical initiator includes at least one of 2,3-dimethyl-2,3-diphenylbutane and poly-1,4-diisopropylbenzene.

[0044]

[12] The polyolefin resin foamed particles according to

[11] , wherein the radical initiator is selected from 2,3-dimethyl-2,3-diphenylbutane.

[0045]

[13] The polyolefin resin foamed particles according to any one of [1] to

[12] , wherein the polyolefin resin is a polypropylene resin.

[0046]

[14] The polyolefin resin foamed particles according to any one of the technical solutions [1] to

[13] , wherein the polyolefin resin foamed particles are obtained by dispersing polyolefin resin particles in an aqueous dispersion medium in a closed container, heating the polyolefin resin particles to a temperature above the softening temperature of the polyolefin resin particles in the presence of a foaming agent, and then releasing the resulting mixture into an environment with a pressure lower than the internal pressure of the closed container, wherein the polyolefin resin particles include a polyolefin resin, an inorganic hypophosphite and a melamine-based flame retardant, and the content of the inorganic hypophosphite is 1.6 to 10.0 parts by weight, and the content of the melamine-based flame retardant is 0.01 to 2.0 parts by weight relative to 100 parts by weight of the polyolefin resin.

[0047]

[15] The polyolefin resin foamed particles according to any one of [1] to

[14] , wherein the foaming ratio of the polyolefin resin foamed particles is 5 to 45 times.

[0048]

[16] A method for preparing polyolefin resin foamed particles, wherein the method comprises dispersing polyolefin resin particles in an aqueous dispersion medium in a closed container, heating the mixture to a temperature above the softening temperature of the polyolefin resin particles in the presence of a foaming agent, and then releasing the resulting mixture into an environment having a pressure lower than the internal pressure of the closed container to foam the polyolefin resin particles to obtain the polyolefin resin foamed particles;

[0049] The polyolefin resin particles include polyolefin resin, inorganic hypophosphite and melamine flame retardant. Relative to 100 parts by weight of the polyolefin resin, the content of the inorganic hypophosphite is 1.6 to 10.0 parts by weight, and the content of the melamine flame retardant is 0.01 to 2.0 parts by weight.

[0050]

[17] A polyolefin resin foamed molded product obtained by in-mold foaming of the polyolefin resin foamed particles described in any one of [1] to

[15] or the polyolefin resin foamed particles obtained according to the preparation method of

[16] .

[0051]

[18] The polyolefin resin foam molded product according to

[17] , wherein the polyolefin resin foam molded product meets UL94 HF-1 grade and has an oxygen index of not less than 27%.

[0052]

[19] The polyolefin-based resin foam molded product according to

[17] or

[18] , wherein the polyolefin-based resin foam molded product has a density of 25 to 95 g / L.

[0053]

[20] An interior material for public transportation, comprising the polyolefin resin foam molding according to any one of the technical solutions

[17] to

[19] .

[0054]

[21] The interior material of a public transportation vehicle according to

[20] , wherein the public transportation vehicle includes a high-speed railway and / or an airplane.

[0055]

[22] Use of the polyolefin resin foam molding as described in any of the technical solutions

[17] to

[19] in the preparation of high-speed railway seats.

[0056] Effects of the Invention

[0057] The polyolefin resin foamed particles of the present invention can obtain in-mold foamed products with good in-mold foaming moldability and surface appearance as good as before and showing excellent flame retardancy, which reaches HF-1 grade in the horizontal flammability test (UL94HF) of UL94 foamed materials, and also has a good oxygen index. In some specific embodiments of the present invention, the oxygen index is not less than 27%, and in other specific embodiments of the present invention, the oxygen index is above 28%, and more preferably, the oxygen index is above 29%. It can reduce the generation of harmful gases during combustion, and is particularly suitable for the field of interior materials of public transportation vehicles, especially high-speed transportation vehicles. DETAILED DESCRIPTION

[0058] The following describes the embodiments of the present invention, but the present invention is not limited thereto. The present invention is not limited to the various structures described below, and various changes can be made within the scope of the invention claim, and the embodiments and embodiments obtained by appropriately combining the technical means disclosed in different embodiments and embodiments are also included in the technical scope of the present invention. In addition, all the documents recorded in this specification are cited in this specification as references.

[0059] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0060] In this specification, "foamed material" refers to a material obtained through a foaming process. In particular, a foamed body obtained by in-mold foam molding is referred to as an "in-mold foamed body". In the case of a material obtained through a foaming process before in-mold foam molding, it is referred to as a pre-foamed material. In addition, a granular pre-foamed material is referred to as a "resin foamed particle" or "pre-foamed particle". "Foamed body" and "foamed product" refer to products obtained from a foamed material or a foamed body.

[0061] In the context of describing the invention (especially in the context of the following claims), the terms "a", "an", and "the" and similar language are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0062] In this specification, the numerical range expressed using "numerical value A to numerical value B" or "numerical value A-numerical value B" means a range including the endpoints numerical values ​​A and B.

[0063] In this specification, the meaning of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process. In this specification, "optional" or "optionally" means that the event or situation described below may or may not occur, and the description includes the situation where the event occurs and the situation where the event does not occur.

[0064] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "some specific / preferred technical solutions", "other specific / preferred technical solutions", etc. refer to the specific elements (e.g., features, structures, properties and / or characteristics) related to the embodiments described herein being included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0065] The term "comprising" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products or devices.

[0066] The polyolefin resin foamed particles of the present invention include polyolefin resin, inorganic hypophosphite and melamine flame retardant. In some specific embodiments of the present invention, the polyolefin resin foamed particles are obtained by foaming polyolefin resin particles, that is, the polyolefin resin particles include polyolefin resin, inorganic hypophosphite and melamine flame retardant. Relative to 100 parts by weight of the polyolefin resin, the content of the inorganic hypophosphite is 1.6 to 10.0 parts by weight, and the content of the melamine flame retardant is 0.01 to 2.0 parts by weight. The inventors surprisingly found that adding a specific content of inorganic hypophosphite and melamine flame retardant to the polyolefin resin can obtain foamed particles that exhibit high flame retardancy and good fusion during in-mold molding, and can obtain polyolefin resin foamed particles and in-mold molded bodies with excellent surface appearance, and the obtained in-mold molded bodies also have a high oxygen index (more than 27%) and reach UL94 HF-1 grade. In this specification, "reaching UL94 HF-1 grade" means that the polyolefin resin foam molding can reach the HF-1 flame retardancy level through the UL94 foam material horizontal flammability test, but it does not mean that it needs to pass the UL94 HF-1 certification.

[0067] Hereinafter, each component will be described in sequence.

[0068] Polyolefin resin

[0069] Polyolefin resin refers to a polymer obtained by polymerizing or copolymerizing α-olefins (i.e., monoolefins with double bonds at the ends of the molecular chain, molecular formula R-CH=CH2, where R is an alkyl group) such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, etc., and certain cycloolefins, while polystyrene resin does not belong to the category of polyolefin resin. Furthermore, the polyolefin resin used in the present invention is a polymer containing more than 75% by weight of α-olefin monomers. The content of α-olefin monomers is preferably more than 80% by weight. It may also contain less than 25% by weight, preferably less than 20% by weight, of other monomers copolymerizable with α-olefin monomers.

[0070] Specific examples of the α-olefin monomer include α-olefins having 2 to 12 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, and 1-decene. These may be used alone or in combination of two or more.

[0071] Specific examples of other monomers copolymerizable with the α-olefin monomer include cyclopentene, norbornene, cyclic olefins such as 1,4,5,8-dimethano-1,2,3,4,4a,8,8a,6-octahydronaphthalene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, and dienes such as 7-methyl-1,6-octadiene. These monomers may be used alone or in combination of two or more.

[0072] As the specific example of the polyolefin resin used in the present invention, for example, polyethylene resins with ethylene as the main component, and polypropylene resins with propylene as the main component, such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, can be listed. These polyolefin resins can be used alone, or two or more can be used in combination. Among these, as the polyolefin resin, from aspects such as mechanical strength and heat resistance, it is preferred to use a polypropylene resin.

[0073] Here, the "polypropylene resin" used in the present invention refers to a polymer obtained by polymerizing propylene as at least a part of the monomer, and the propylene content exceeds 50% by weight in 100% by weight. As long as it contains propylene as the main component of the monomer, it is not particularly limited, and examples thereof include propylene homopolymers, α-olefin-propylene random copolymers, α-olefin-propylene block copolymers, etc. They can be used alone or in combination of two or more. As a copolymer of propylene and α-olefin, for example, it can be a copolymer of propylene and an α-olefin having 4 to 10 carbon atoms. As the above-mentioned α-olefin having 4 to 10 carbon atoms, for example, 1-butene, 1-pentene, 1-hexene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-octene, etc. can be cited.

[0074] Among these polymers, ethylene / propylene random copolymers and ethylene / 1-butene / propylene random copolymers are preferred from the viewpoint of good foaming properties and good moldability. In the polypropylene resin, the preferred ethylene content is 1 wt% or more and 10 wt% or less, more preferably 2 wt% or more and 7 wt% or less, more preferably 3.5 wt% or more and 6 wt% or less, and particularly preferably 3.5 wt% or more and 5 wt% or less. In addition, the ethylene content of the comonomer component in the polypropylene resin can be adjusted using 13 C-NMR determination.

[0075] The melting point of the polypropylene resin used in the present invention is preferably 130°C to 165°C, more preferably 135°C to 155°C. When the melting point of the polypropylene resin is lower than 130°C, there is a tendency that the heat resistance and mechanical strength are insufficient. In addition, when the melting point exceeds 165°C, there is a tendency that it is difficult to ensure fusion during in-mold foaming. The above-mentioned melting point refers to the peak temperature of the endothermic peak in the DSC curve obtained when 1 to 10 mg of the polypropylene resin is heated from 40°C to 220°C at a heating rate of 10°C / min using a differential scanning calorimeter, then cooled to 40°C at a cooling rate of 10°C / min, and then heated to 220°C at a heating rate of 10°C / min again.

[0076] The melt flow rate (hereinafter referred to as "MFR value") of the polypropylene resin used in the present invention is preferably 0.5 g / 10 minutes or more and 30 g / 10 minutes or less, and more preferably 2 g / 10 minutes or more and 20 g / 10 minutes or less. When the MFR value is lower than 0.5 g / 10 minutes, it is sometimes difficult to obtain polypropylene resin foamed particles with a high expansion ratio, and when it exceeds 30 g / 10 minutes, there is a tendency that the bubbles of the polypropylene resin foamed particles are easily broken and the continuous cell rate of the polypropylene resin foamed particles becomes high.

[0077] The MFR value of the polypropylene resin is a value measured under the conditions of a temperature of 230° C. and a load of 2.16 kg in accordance with JIS K7210.

[0078] The ratio (Mw / Mn) of the weight average molecular weight (hereinafter, sometimes described as "Mw") and the number average molecular weight (hereinafter, sometimes described as "Mn") of the polypropylene resin used in the present invention is not particularly limited, but is preferably 3.0 or more, particularly preferably 3.0 or more and 6.0 or less. Mw and Mn can be measured by conventional GPC.

[0079] In the raw materials for preparing polypropylene resin particles, in addition to polypropylene resin, other types of polyolefins, such as polyethylene resin, etc. can also be contained. High-density polyethylene resin, medium-density polyethylene resin, low-density polyethylene resin, linear low-density polyethylene resin, etc. can be listed. In order to increase the foaming ratio, linear low-density polyethylene (or straight-chain low-density polyethylene, sometimes abbreviated as "LLDPE") is preferably used. The other types of polyolefins can be used alone or two or more can be used at the same time. When the other types of polyolefins are used in the present invention, the content of the polypropylene resin is 80% by weight or more, preferably 90% by weight or more, and more preferably 95% by weight or more, based on the total weight of the polyolefin resin.

[0080] In other optional embodiments of the present invention, the polyolefin resin may also be a polyethylene resin. As the polyethylene resin used in the present invention, ethylene homopolymers, ethylene-α-olefin random copolymers, ethylene-α-olefin block copolymers, low-density polyethylene, high-density polyethylene, linear low-density polyethylene, etc. can be listed. As the α-olefins mentioned here, α-olefins with 3 to 15 carbon atoms can be listed, which can be used alone or in combination with more than two kinds. Among these polyethylene resins, when it is an ethylene-α-olefin block copolymer and the comonomer content other than ethylene is 1 to 10 weight %, or when it is a linear low-density polyethylene, it shows good foaming properties and is suitable for use.

[0081] The melting point of the polyethylene resin used in the present invention is preferably 110°C to 140°C, more preferably 120°C to 130°C, because foamed particles having excellent foamability and moldability, and excellent mechanical strength and heat resistance when formed into a polyolefin resin in-mold foamed molded body can be obtained. The above melting point refers to the peak temperature of the endothermic peak in the DSC curve obtained by heating 1 to 10 mg of the polyethylene resin from 40°C to 200°C at a heating rate of 10°C / min, cooling to 40°C at a cooling rate of 10°C / min, and heating again to 200°C at a heating rate of 10°C / min using a differential scanning calorimeter.

[0082] The MFR value of the polyethylene resin used in the present invention is preferably 0.5g / 10 minutes or more and 30g / 10 minutes or less, more preferably 1g / 10 minutes or more and 5g / 10 minutes or less, and most preferably 1.5g / 10 minutes or more and 2.5g / 10 minutes or less. When the MFR value of polyethylene is less than 0.5g / 10 minutes, it is difficult to obtain foamed particles with a high expansion ratio, and the bubbles tend to become uneven. In addition, when the MFR value exceeds 30g / 10 minutes, although it is easy to foam, there is a tendency that the bubbles are easy to break, the continuous bubble rate of the foamed particles becomes high, and there is a tendency that the bubbles also become uneven. The MFR value of the polyethylene resin is a value measured according to JIS K7210 at a temperature of 190°C and a load of 2.16kg.

[0083] The polyolefin resin used in the present invention can be obtained using catalysts such as Ziegler catalysts, metallocene catalysts, and post-metallocene catalysts. If a Ziegler catalyst is used, there is a tendency to obtain a polymer having a large Mw / Mn. In addition, if the polymer obtained using these catalysts is oxidatively decomposed with an organic peroxide, properties such as molecular weight and melt flow rate can be adjusted.

[0084] The polyolefin resin used in the present invention is preferably in an uncrosslinked state, but may be crosslinked by treating with an organic peroxide, radiation or the like.

[0085] Inorganic hypophosphite

[0086] Inorganic hypophosphite belongs to inorganic phosphorus flame retardant. As the main flame retardant in the present invention, it has high phosphorus content, and its flame retardant mechanism combines gas phase flame retardant and condensed phase flame retardant mechanism. It is an effective free radical terminator and carbon forming agent. Due to its good thermal stability, good water resistance, and small effect on the mechanical properties of polymers, it is applied to foamed plastics with good effect. Compared with organic hypophosphite with organic groups, the inorganic hypophosphite of the present invention can significantly reduce toxicity and production cost.

[0087] The inorganic hypophosphite of the present invention can be specifically listed as: aluminum hypophosphite (abbreviated as ALHP, chemical formula: Al(H2PO2)3), sodium hypophosphite, magnesium hypophosphite, zinc hypophosphite, calcium hypophosphite, etc. These compounds can be used alone or in combination of two or more. In a specific embodiment of the present invention, aluminum hypophosphite is used as the main flame retardant, which has better flame retardancy and thermal stability.

[0088] Regarding the content of the inorganic hypophosphite in the present invention, relative to 100 parts by weight of the polyolefin resin, its content is 1.6 to 10.0 parts by weight. At this time, the polyolefin foaming molded body prepared from the polyolefin resin particles can perform well in both flame retardancy and moldability, and has the HF-1 grade according to the horizontal flammability test of UL94 foaming materials, namely the UL94HF test method, and at the same time satisfies the oxygen index of not less than 27%. If the content of the inorganic hypophosphite is less than 1.6 parts by weight, the flame retardant effect is not obvious and the UL94 HF-1 grade cannot be achieved. If it is more than 10.0 parts by weight, it will have an adverse effect on the dispersion stability and the size of the foam cells during supercritical foaming, and the attachment of the inorganic component to the surface of the foamed particles will further affect the moldability. In some specific embodiments of the present invention, in order to have the HF-1 grade and satisfy the oxygen index of not less than 28%, the content of the inorganic hypophosphite is 1.8 to 4.0 parts by weight. In other specific embodiments of the present invention, the content of the inorganic hypophosphite is 1.8 to 3.8 parts by weight, further 2.0 to 3.7 parts by weight.

[0089] Melamine flame retardant

[0090] Melamine flame retardants, also known as melamine-based flame retardants, refer to flame retardants containing melamine structures, which have excellent thermal stability, high carbonization, and good flame retardant and smoke suppression effects. The melamine flame retardants of the present invention include melamine sulfate (C3H8N6O4S, CAS: 84962-53-8), melamine polyphosphate (C3H6N6.(H3PO4) n , CAS: 218768-84-4), melamine cyanurate (C6H9N9O3, CAS: 37640-57-6), melamine pyrophosphate (C3H 10 N6O7P2, CAS: 15541-60-3), melamine hydrobromide (C3H6N6.(HBr) x , CAS: 29305-12-2) or more. In some embodiments of the present invention, the melamine flame retardant is selected from melamine hydrobromide (hereinafter, sometimes referred to as "MHB"), which has the advantages of both nitrogen-based and bromine-based flame retardants. When X=1, the molecular formula is as follows:

[0091]

[0092] In the present invention, the inventors surprisingly found that adding a small amount of melamine flame retardant can produce flame retardant synergistic effect with inorganic hypophosphite, so that the polyolefin resin foaming molding of the present invention has good flame retardancy and can also meet the requirements of safety and environmental protection. In the present invention, the content of melamine flame retardant is 0.01 to 2.0 parts by weight relative to 100 parts by weight of polyolefin resin. In some specific embodiments of the present invention, the content of melamine flame retardant is 0.01 to 1.0 parts by weight relative to 100 parts by weight of polyolefin resin. In order to further control the halogen content in the final product, it is preferred that the content of melamine flame retardant does not exceed 0.3 parts by weight. In other specific embodiments of the present invention, the content of melamine flame retardant is 0.02 to 0.16 parts by weight. In some specific embodiments of the present invention, the weight ratio of inorganic hypophosphite to melamine flame retardant is greater than 20, and further the weight ratio of inorganic hypophosphite to melamine flame retardant is 25 to 27. If the content of melamine flame retardant is too high or the content ratio of inorganic hypophosphite to melamine flame retardant is too low, it will cause environmental problems on the one hand, and will affect the flame retardant grade and / or oxygen index of the foam on the other hand.

[0093] Other flame retardant components

[0094] In order to further improve the oxygen index and stability, in a preferred embodiment of the present invention, the polyolefin resin particles optionally further include a compound represented by the general formula (1):

[0095] R 1 NHCH2CH2CH2NR 2 CH2CH2NR 3 CH2CH2CH2NHR 4 (1)

[0096] In the general formula (1), R 1 , R 2 is a group represented by the general formula (2), the dotted line above the triazine ring represented by the general formula (2) represents the connection portion with the nitrogen atom in the general formula (1), R 3 and R 4 One of them is a group represented by the general formula (2), the dotted line above the triazine ring represented by the general formula (2) represents the connection part with the nitrogen atom in the general formula (1), R 3 and R 4 The other side is a hydrogen atom. In the general formula (2), R 5 is an alkyl group having 1 to 12 carbon atoms, R 6 is methyl, cyclohexyl or octyl,

[0097]

[0098] In the general formula (2), R 5 represents an alkyl group having 1 to 12 carbon atoms such as methyl, ethyl, propyl, butyl, n-pentyl, n-hexyl, n-heptyl, nonyl, decyl, undecyl, dodecyl, isopropyl, isobutyl, sec-butyl, tert-butyl, 2-ethylbutyl, isopentyl, 1-methylpentyl, 1,3-dimethylbutyl, 1-methylhexyl, isoheptyl, 1,1,3,3-tetramethylpentyl, 1-methylundecyl, 1,1,3,3,5,5-hexamethylhexyl, etc., and R 6 represents a methyl group, a cyclohexyl group or an octyl group. Specific examples of the group represented by the general formula (2) include groups derived from 2,4-bis[(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazine, 2,4-bis[(1-oxocyclohexyl-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.

[0099] The compound represented by the general formula (1) belongs to the sterically hindered amine ether compound, and specific examples thereof include: N,N',N"'-tris{2,4-bis[(1-oxocyclohexyl-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazine-6-yl}-3,3'-ethylenediiminopropylamine, N,N',N"-tris{2,4-bis[(1-oxocyclohexyl-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazine-6-yl}-3,3'-ethylenediiminobispropylamine, N,N',N"'-tris{2,4-bis[(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazine -6-yl}-3,3'-ethylenediiminobispropylamine, N,N',N"-tris{2,4-bis[(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazin-6-yl}-3,3'-ethylenediiminopropylamine, N,N',N"'-tris{2,4-bis[(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazin-6-yl}-3,3'-ethylenediiminopropylamine, N,N',N"-tris{2,4-bis[(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylamino]-s-triazin-6-yl}-3,3'-ethylenediiminopropylamine, etc. These compounds may be used alone or in combination of two or more.

[0100] The compound represented by the general formula (1) in the present invention is determined whether to be added according to the needs of the actual application field. In some specific embodiments of the present invention, considering flame retardancy and cost, the compound represented by the general formula (1) is preferably 0.01 to 2.0 parts by weight, more preferably 0.10 to 1.5 parts by weight, and even more preferably 0.20 to 1.0 parts by weight relative to 100 parts by weight of polyolefin resin particles. If the amount of the compound represented by the general formula (1) added is too much, on the one hand, there is a trend of rising costs, and on the other hand, it may have an adverse effect on the oxygen index of the foam.

[0101] In another preferred embodiment of the present invention, the polyolefin resin particles of the present invention further include a brominated flame retardant (excluding the aforementioned melamine flame retardant), such as one or more brominated flame retardants in brominated bisphenol A flame retardants, brominated bisphenol S flame retardants, brominated butadiene-styrene block copolymer flame retardants, and brominated polyphenylene ether flame retardants. In order to obtain a higher oxygen index, brominated bisphenol A flame retardants and / or brominated bisphenol S flame retardants such as bis(alkyl ether) tetrabromobisphenol A flame retardants and / or bis(alkyl ether) tetrabromobisphenol S flame retardants are preferred, and brominated bisphenol S flame retardants are more preferred. In some specific embodiments of the present invention, the additional brominated flame retardants can specifically include: one or more of tetrabromobisphenol A, tetrabromobisphenol S, tetrabromobisphenol A-bis(2,3-dibromopropyl ether) (TBAB, also known as octabromoether), tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A-diglycidyl ether and / or tetrabromobisphenol S-bis(2,3-dibromo-2-methylpropyl ether) (TBSB).

[0102] In the present invention, the content of the brominated flame retardant is 0.1 to 5.0 parts by weight, preferably 0.2 to 3.0 parts by weight, and further preferably 0.2 to 1.5 parts by weight, relative to 100 parts by weight of the polyolefin resin.

[0103] In another preferred embodiment of the present invention, the polyolefin resin particles of the present invention further include a free radical initiator to further improve the flame retardancy of the polyolefin resin in-mold foamed article.

[0104] As the free radical initiator used in the present invention, for example, 2,3-dimethyl-2,3-diphenylbutane, poly-1,4-diisopropylbenzene, 2,3-diethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, 3,4-diethyl-3,4-diphenylhexane, 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-ethyl-1-pentene, etc., also include dicumyl peroxide peroxide. Among these free radical initiators, a free radical initiator that is stable under the resin processing temperature conditions is preferred, specifically, at least one of 2,3-dimethyl-2,3-diphenylbutane and poly-1,4-diisopropylbenzene is preferred. In some specific embodiments of the present invention, the free radical initiator is selected from 2,3-dimethyl-2,3-diphenylbutane (DMDPB for short, also known as dicumyl). As for the content of the free radical initiator in the present invention, in some specific embodiments of the present invention, the free radical initiator is 0.01 to 0.5 parts by weight relative to 100 parts by weight of the polyolefin resin. In other specific embodiments of the present invention, the free radical initiator is 0.02 to 0.2 parts by weight relative to 100 parts by weight of the polyolefin resin. In other specific embodiments of the present invention, the free radical initiator is 0.03 to 0.15 parts by weight relative to 100 parts by weight of the polyolefin resin.

[0105] Other components

[0106] In order to obtain a black molded body, the polyolefin resin particles used to form the polyolefin resin foamed particles of the present invention contain carbon black.

[0107] Specific examples of carbon black that can be used in the present invention include channel black, roller black, disc black, gas furnace black, oil furnace black, thermal black, acetylene black, etc. These carbon blacks can be used alone or in combination of two or more.

[0108] In the polyolefin resin particles of the present invention, the content of carbon black is preferably 0.5 parts by weight or more and 20 parts by weight or less relative to 100 parts by weight of the polyolefin resin particles. In some specific embodiments of the present invention, the content of carbon black is 0.5 to 2 parts by weight. If the content of carbon black is less than 0.5 parts by weight, it tends to be difficult to fully blacken. If it exceeds 20 parts by weight, the bubble diameter of the obtained polyolefin resin foamed particles tends to be miniaturized, which not only leads to a tendency to deteriorate the in-mold foaming formability (especially the surface appearance), but also leads to a tendency to be difficult to obtain sufficient flame retardancy.

[0109] In the present invention, carbon black and polyolefin resin can be directly mixed, or a carbon black masterbatch can be prepared first, that is, carbon black and polyolefin resin are melt-kneaded together to prepare a polyolefin resin in which carbon black is dispersed. Polyolefin resins for preparing carbon black masterbatch include polyethylene resins and polypropylene resins.

[0110] The polyolefin resin particles may also contain a foaming nucleating agent (hereinafter referred to as nucleating agent) that promotes the formation of bubble nuclei. As the nucleating agent used in the present invention, for example, inorganic nucleating agents such as talc, calcium stearate, calcium carbonate, silicon dioxide, kaolin, titanium oxide, bentonite, barium sulfate, and zinc borate can be listed. They can be used alone or in combination of two or more. Among these nucleating agents, talc, calcium carbonate and calcium stearate are preferred, which are cheap and convenient for obtaining uniform bubbles. The amount of the nucleating agent added in the present invention varies depending on the type of foaming agent used. Generally speaking, the amount of the nucleating agent added is 0.005 to 2 parts by weight relative to 100 parts by weight of the polyolefin resin, and more preferably, 0.01 to 1 part by weight. When the amount of the nucleating agent added is less than 0.005 parts by weight, there is a tendency that is not conducive to sufficient foaming. When the amount of the nucleating agent added exceeds 2 parts by weight, there is a tendency that the average bubble diameter of the polyolefin resin foamed particles becomes too small and the in-mold foaming moldability becomes poor.

[0111] The polyolefin resin pellets may contain a heat stabilizer, a light stabilizer, a colorant, an antistatic agent, a radiation heat transfer inhibitor, other flame retardants, a lubricant, a filler, etc., as needed without impairing the effects of the present invention.

[0112] In the present invention, the heat stabilizer may be a hindered amine compound, a phosphorus compound or an epoxy compound. Examples of the light stabilizer include hindered amines, phosphorus stabilizers, epoxy compounds, phenolic antioxidants, nitrogen-containing stabilizers, sulfur stabilizers, benzotriazoles and the like.

[0113] Examples of the colorant used in the present invention include inorganic pigments such as carbon black, Ketjen black, iron black, cadmium yellow, cadmium red, cobalt violet, cobalt blue, Prussian blue, ultramarine blue, chrome yellow, zinc yellow, barium yellow, etc.; organic pigments such as polyazo, quinacridone, phthalocyanine, perinone, anthraquinone, thioindigo, diquinazine, isoindolinone and quinophthalone.

[0114] There are no particular restrictions on the antistatic agent used in the present invention, and examples thereof include low molecular weight antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds, and aliphatic ethanolamide compounds, and high molecular weight antistatic agents. These antistatic agents can be used alone or in combination of two or more. For example, a commercially available mixture of octadecyldiethanolamine monostearate and octadecyldiethanolamine includes Electro Stripper TS-11B, and a commercially available mixture of octadecyldiethanolamine monostearate, octadecyldiethanolamine, and aliphatic alcohol includes Electro Stripper TS-15B. The content of the antistatic agent in the present invention is preferably 0.1 to 3 parts by weight, particularly preferably 0.2 to 2 parts by weight, relative to 100 parts by weight of the polyolefin resin. When the content of the antistatic agent is less than 0.1 parts by weight, there is a tendency that the antistatic performance is difficult to exert, and when it exceeds 3 parts by weight, there is a tendency that the deformation shrinkage rate of the obtained foamed molded body is large and the stretching of the molded body surface is deteriorated.

[0115] The present invention is used for radiative heat transfer inhibitors (materials having the characteristics of reflecting, scattering or absorbing light in the near-infrared or infrared fields (for example, a wavelength range of 800 to 3000 nm)), such as graphite, graphene, activated carbon, carbon black, titanium dioxide and metallic aluminum.

[0116] Method for preparing polyolefin resin particles

[0117] The polyolefin resin particles used in the present invention are obtained by the following method: using an extruder, a kneader, a Banbury mixer, a roller press, etc., a polyolefin resin, an inorganic hypophosphite, a melamine flame retardant, carbon black, a nucleating agent, and other optional flame retardant components or other optional additives such as the compound represented by the general formula (1) are melt-mixed, and then polyolefin resin particles having a cylindrical, elliptical, spherical, cubic, rectangular, etc. shape are obtained. In some specific embodiments of the present invention, flame retardants such as inorganic hypophosphites and melamine flame retardants can be first mixed with polyolefin resins to form flame retardant masterbatches, and then melt-mixed with a large amount of polyolefin resins and other components. In other specific embodiments of the present invention, flame retardants such as inorganic hypophosphites and melamine flame retardants and free radical initiators can also be first mixed and dispersed in polyolefin resins to form a composite flame retardant masterbatch, and then melt-mixed with polyolefin resins and other components.

[0118] In order to obtain foamed particles having an appropriate average maximum diameter, the average particle weight of the polyolefin resin particles of the present invention is preferably 0.1 mg to 30 mg, more preferably 0.3 mg to 10 mg. Here, the average particle weight of the polyolefin resin particles is the average resin particle weight of 100 randomly selected polyolefin resin particles.

[0119] <Polyolefin Resin Foamed Particles>

[0120] The polyolefin resin foamed particles of the present invention are obtained by foaming the polyolefin resin particles described above. Specifically, the polyolefin resin foamed particles of the present invention are obtained by dispersing the polyolefin resin particles described above in an aqueous dispersion medium in a closed container, heating the polyolefin resin particles to a temperature above the softening temperature of the polyolefin resin particles in the presence of a foaming agent, and then releasing the resulting mixture into an environment having a pressure lower than the internal pressure of the closed container.

[0121] In some specific embodiments of the present invention, the foaming agent is water and / or inorganic gas such as carbon dioxide, air, nitrogen, etc., which can be used alone or in combination. They have a small environmental load and no combustion hazard, among which carbon dioxide is further preferred.

[0122] As the aqueous dispersion medium used in the present invention, it is preferred to use only water, but a dispersion medium in which methanol, ethanol, ethylene glycol, glycerol, etc. are added to water can also be used. It should be noted that when the present invention contains a hydrophilic compound, the water in the aqueous dispersion medium also acts as a foaming agent, which helps to increase the foaming ratio. In order to prevent the adhesion of polyolefin resin particles to each other, it is preferred to use a dispersant in the aqueous dispersion medium. As the dispersant used in the present invention, inorganic dispersants such as calcium phosphate, magnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, and clay can be exemplified. These dispersants can be used alone or in combination of two or more. The present invention further preferably uses a dispersant together with a dispersant. As examples of the dispersant used in the present invention, for example, carboxylate types such as N-acylamino acid salts, sulfonate types such as alkylbenzene sulfonates, sulfate ester types such as alkyl allyl ether sulfates, or polycarboxylic acid type polymer surfactants such as maleic acid copolymer salts and polyacrylic acid salts can be cited. These dispersants can be used alone or in combination of two or more. Among these, it is preferred to use at least one selected from calcium phosphate, magnesium phosphate, barium sulfate or kaolin as a dispersant and at least one selected from sodium n-alkane sulfonate and sodium alkylbenzene sulfonate (such as DBS) as a dispersing aid. The amount of the dispersant and dispersing aid used in the present invention varies depending on their type, the type and amount of the polyolefin resin particles used. Generally, it is preferred to add 0.2 to 2.5 parts by weight of the dispersant relative to 100 parts by weight of the aqueous dispersion medium, and it is more preferred to add 0.005 to 0.08 parts by weight of the dispersing aid. In order to make the polyolefin resin particles more dispersible in the aqueous dispersion medium, it is preferred to add 25 to 90 parts by weight of polyolefin resin particles relative to 100 parts by weight of the aqueous dispersion medium.

[0123] In some specific embodiments of the present invention, the heating temperature in the sealed container is preferably above the melting point of the polyolefin resin particles -25°C and below the melting point of the polyolefin resin particles +25°C, more preferably above the melting point of the polyolefin resin particles -15°C and below the melting point of the polyolefin resin particles +15°C. Heating and pressurizing are performed at this temperature to impregnate the polyolefin resin particles with a foaming agent. In some specific embodiments of the present invention, the foaming temperature is 150 to 160°C, further 154 to 160°C. In some specific embodiments of the present invention, the foaming pressure is 1.3 to 2.2Mpa, further 1.3 to 1.8Mpa, and further 1.4 to 1.7Mpa.

[0124] The sealed container for dispersing the polyolefin resin pellets is not particularly limited as long as it can withstand the internal pressure and temperature of the container during the production of the polyolefin resin pellets. For example, it is a hot press type container.

[0125] The expansion ratio of the polyolefin resin foamed particles obtained by the above-mentioned manufacturing method is not less than 5 times and not more than 45 times. The expansion ratio of the polyolefin resin foamed particles will affect the density of the molded body (the higher the expansion ratio, the relatively lower the density of the molded body), and further have a certain impact on the flame retardant properties of the molded body (especially the oxygen index). In some specific embodiments of the present invention, the expansion ratio of the polyolefin resin foamed particles is 8 to 45 times, further 9 to 40 times, and further 10 to 38 times. Here, the calculation method of the expansion ratio is as follows: Calculate the weight w (g) of the polyolefin resin foamed particles and the drainage volume v (cm 3 ), and the density d (g / cm 3 ) to calculate the foaming ratio.

[0126] Foaming ratio = d × v / w

[0127] In addition, polyolefin resin foam particles with a high foaming ratio can also be obtained by the following secondary foaming method, etc.: first, polyolefin resin foam particles with a foaming ratio of 5 times to 35 times are manufactured, and the polyolefin resin foam particles are placed in a sealed container, and nitrogen, air, etc. are introduced into the container by pressurizing, thereby making the pressure inside the polyolefin resin foam particles higher than normal pressure, and then the polyolefin resin foam particles are heated by steam, etc., so as to further foam them.

[0128] <Polyolefin-based resin foamed article>

[0129] In the present invention, the polyolefin resin foam molded article can be obtained by performing in-mold foam molding in which the polyolefin resin foamed particles obtained as described above are filled in a mold and heated with steam or the like to fuse the foamed particles together.

[0130] When the polyolefin resin foamed particles of the present invention are subjected to in-mold foaming, the following conventionally known methods can be used:

[0131] (a) directly using foamed particles for forming;

[0132] (b) pre-pressing inorganic gas such as air into the foaming particles to impart foaming potential energy;

[0133] (c) Filling the compressed foamed particles into a mold for molding.

[0134] In the present invention, when a method of pre-pressing inorganic gas such as air into the foamed particles to impart foaming potential energy is adopted (hereinafter sometimes referred to as "internal pressure imparting method"), it is preferred to impart an internal pressure of less than 3.0 atm to the polyolefin resin foamed particles, more preferably an internal pressure of more than 1.3 atm and less than 3.0 atm, and further preferably an internal pressure of more than 1.5 atm and less than 2.5 atm. If the imparted internal pressure exceeds 3.0 atm, not only will the time for imparting the internal pressure in the pressure vessel increase, but the required cooling time during in-mold forming will also increase, so there is a tendency for the molding cycle to become longer and productivity to decrease. In addition, if the imparted internal pressure is lower than 1.3 atm, gaps between particles will appear on the surface of the molded body after in-mold forming, or surface unevenness, shrinkage of the molded body, and surface wrinkles will occur. For in-mold molded bodies with ridges, this will result in poor filling of the foamed particles and a tendency for voids to occur.

[0135] Regarding the method of imparting internal pressure to the polyolefin resin foamed particles, for example, the polyolefin resin foamed particles can be filled into a pressure-resistant container, and then pressurized using an inorganic gas. At this time, heating can also be performed as needed. Here, the above-mentioned pressure-resistant container is not particularly limited, and for example, it can be a hot-pressed pressure-resistant container. The above-mentioned inorganic gas is, for example, air, nitrogen, argon, helium, etc., but air and nitrogen with low cost are preferred.

[0136] Regarding the specific method of making the polyolefin resin foamed particles of the present invention into a polyolefin resin in-mold foamed body by in-mold foaming, for example, there is the following method: the polyolefin resin foamed particles are subjected to air pressure treatment (or air impregnation treatment) in a pressure-resistant container in advance, thereby pressing air into the polyolefin resin foamed particles to give them foaming potential, and then the polyolefin resin foamed particles are filled into a molding space surrounded by two molds that can be closed but not sealed, and water vapor is used as a heating medium, and the hot water vapor pressure of 0.10 to 0.4 MPa and the heating time of 3 to 30 seconds are used to form the polyolefin resin foamed particles so that the polyolefin resin foamed particles are fused with each other, and then the mold is cooled by water cooling, and finally the mold is opened to obtain the polyolefin resin in-mold foamed body. In some specific embodiments of the present invention, the air impregnation treatment applies 0.19 to 0.23 MPa, the steam pressure is 0.30 MPa / 0.31 MPa, the double-sided pressure is slightly different, and the heating time is 20 to 25 seconds.

[0137] The density of the polyolefin resin in-mold foamed body obtained using the polyolefin resin foamed particles of the present invention is preferably 10 g / L to 150 g / L, more preferably 20 g / L to 100 g / L, and further preferably 25 g / L to 95 g / L, which is conducive to obtaining products with high flame retardancy.

[0138] <Purpose>

[0139] The polyolefin resin in-mold foamed body thus obtained can have excellent moldability and flame retardancy, good appearance of the molded body, high fusion rate, can be suitable for HF-1 in the horizontal test of UL94 foam body (or reach UL94 HF-1 grade or be qualified in the HF-1 test according to UL94), and can also have a high oxygen index. In some embodiments of the present invention, the oxygen index reaches more than 27%, and in some preferred embodiments, the oxygen index reaches more than 28%, or even reaches more than 30%, so that the polyolefin resin foamed particles and polyolefin resin foamed bodies of the present invention can meet the requirements of the interior materials of public transportation vehicles. The polyolefin resin foamed particles and polyolefin resin foamed bodies of the present invention are particularly suitable for preparing elastic cushion materials such as seat cores on high-speed public transportation vehicles (such as high-speed railways, airplanes, etc.). In international standards, railways with a speed of more than 200km / h and a speed of 250km / h under construction are high-speed railways (i.e., high-speed railways for short). In China, high-speed railways generally refer to railway systems that can provide trains with a maximum speed of more than 200km / h.

[0140] Therefore, the present invention also provides interior materials for public transportation vehicles based on the above-mentioned polyolefin-based resin foam moldings, such as elastic cushioning materials for high-speed railways. In a specific embodiment of the present invention, the polyolefin-based resin in-mold foam molding of the present invention is used to prepare the inner core of a high-speed railway seat, and its horizontal combustion flame retardant grade, oxygen index, smoke density, and smoke toxicity are all qualified, and can meet the requirements of TB / T3237-2010 Technical Conditions for Flame Retardant Interior Materials for EMUs.

[0141] The present invention is further illustrated by the following examples, but is not intended to be limiting.

[0142] Next, the present invention will be described based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0143] Example

[0144] <Example 1>

[0145] [Preparation of polypropylene resin particles]

[0146] 1.60 parts by weight of aluminum hypophosphite (ALHP) and 4.80 parts by weight of propylene-ethylene random copolymer (ethylene content: 2.2 weight%, MFR: 8.0 g / 10 minutes) were mixed to prepare aluminum hypophosphite flame retardant masterbatch (wherein the mass fraction of aluminum hypophosphite was 25 weight%). 0.06 parts by weight of melamine hydrogen bromide (MHB) and 0.24 parts by weight of propylene-ethylene random copolymer (ethylene content: 2.2 weight%, MFR: 8.0 g / 10 minutes) were mixed to prepare melamine hydrogen bromide flame retardant masterbatch (wherein the mass fraction of MHB was 20 weight%).

[0147] 94.96 parts by weight of propylene-ethylene random copolymer (ethylene content: 2.2% by weight, MFR: 8.0 g / 10 minutes) was mixed with the prepared aluminum hypophosphite flame retardant masterbatch, melamine hydrogen bromide flame retardant masterbatch, 0.06 parts by weight of free radical initiator DMDPB, 0.63 parts by weight of carbon black and 0.87 parts by weight of talc, and the obtained mixture was kneaded by a twin-screw extruder (the extrusion setting temperature was up to 200° C.) to obtain polypropylene resin particles. The average particle weight of the polypropylene resin particles was 1.0 mg.

[0148] [Preparation of polypropylene resin foamed particles]

[0149] In the capacity of 0.01m 3 In a pressure-resistant autoclave (10L), 100 parts by weight of the obtained polypropylene resin particles, 200 parts by weight of water, 0.6 parts by weight of powdered basic tricalcium phosphate and 0.04 parts by weight of sodium n-alkane sulfonate were placed, and carbon dioxide was added under stirring. The generated aqueous dispersion was heated to a foaming temperature of 155°C, and the foaming pressure was pressurized to 1.55MPa by additional introduction of carbon dioxide into the container. Then, while the pressure inside the container was maintained at the pressure by introducing nitrogen, the valve arranged at the lower part of the pressure container was opened, and the aqueous dispersion was released into the atmospheric pressure through a perforated plate having an opening of 3.2mm in diameter, to obtain polypropylene resin foamed particles. The foaming ratio thereof was tested to be 15 times, and the results are shown in Table 1.

[0150] [Preparation of in-mold foamed body]

[0151] After removing the water from the obtained polypropylene resin foamed particles, an internal pressure of 0.21MPa (gauge pressure) was applied by air impregnation treatment, and the particles were filled in a mold of 450mm in length × 350mm in width × 60mm in thickness, and then the foamed particles were heated for 22 seconds with water vapor at a pressure of 0.30-0.31MPa (gauge pressure) to fuse the particles to each other. The obtained polypropylene resin in-mold foamed body was evaluated, and it was found that there was no concave-convex on its surface and there was basically no gap between the particles. The obtained in-mold foamed body was broken and its cross section was observed. The particles that were fully fused with other particles accounted for more than 60%, proving that its fusion rate was excellent.

[0152] The obtained in-mold foamed product was tested and evaluated for its density, flame retardancy level and oxygen index. The results are shown in Table 1.

[0153] <Example 2 to Example 14>, <Comparative Example 1 to Comparative Example 7>

[0154] [Preparation of polypropylene resin particles]

[0155] According to Table 1, the amounts of ALHP and MHB were changed to prepare aluminum hypophosphite flame retardant masterbatch (wherein the mass fraction of aluminum hypophosphite was 25 wt %) and melamine hydrogen bromide flame retardant masterbatch (wherein the mass fraction of MHB was 20 wt %), respectively. The preparation method and steps were the same as those in Example 1.

[0156] A propylene-ethylene random copolymer (ethylene content: 2.2 wt %, MFR: 8.0 g / 10 min) was mixed with the prepared aluminum hypophosphite flame retardant masterbatch, melamine hydrogen bromide flame retardant masterbatch, DMDPB, and an optional sterically hindered amine ether flame retardant compound (manufactured by BASF, FLAMESTAB NOR116FF, referred to as NOR116FF) of the compound represented by the general formula (1) of the present invention, an optional bromine flame retardant (tetrabromobisphenol A-bis(2,3-dibromopropyl) ether (referred to as TBAB) or tetrabromobisphenol S-bis(2,3-dibromopropyl) ether (referred to as TBSB)), carbon black and talc, and the obtained mixture was kneaded by a twin-screw extruder, and the extrusion setting temperature was up to 200° C. to obtain polypropylene resin pellets. The average particle weight of the polypropylene resin pellets was 1.0 mg. Among them, in order to better disperse in the propylene-ethylene random copolymer, TBAB and TBSB can also be mixed with a small amount of propylene-ethylene random copolymer (ethylene content: 2.2 wt%, MFR: 8.0 g / 10 min) to obtain a flame retardant masterbatch (mass fraction of 20 wt%) and then added to the system. The relative amount of each component is shown in Table 1.

[0157] [Preparation of polypropylene resin foamed particles]

[0158] In the capacity of 0.01m 3 In a pressure-resistant autoclave (10L), 100 parts by weight of the obtained polypropylene resin particles, 200 parts by weight of water, 0.6 parts by weight of powdered basic tricalcium phosphate and 0.04 parts by weight of sodium n-alkane sulfonate are placed, and carbon dioxide is added under stirring. The generated aqueous dispersion is heated to a foaming temperature of 154-160°C, and pressurized to a foaming pressure of 1.3-2.2MPa by additional introduction of carbon dioxide into the container. Then, while the pressure inside the container is maintained at this pressure by introducing nitrogen, the valve arranged at the lower part of the pressure container is opened, and the aqueous dispersion is released into the atmospheric pressure through a perforated plate having an opening of 3.2mm in diameter, to obtain polypropylene resin foamed particles, and its foaming ratio is tested. The results are shown in Table 1.

[0159] [Preparation of in-mold foamed body]

[0160] After removing the water from the obtained polypropylene resin foamed particles, an internal pressure of 0.21MPa (gauge pressure) was applied by air impregnation treatment, and the particles were filled in a mold of 450mm in length × 350mm in width × 60mm in thickness, and then the foamed particles were heated for 22 seconds with water vapor at a pressure of 0.30MPa / 0.31MPa (gauge pressure) to fuse the particles to each other. The obtained polypropylene resin in-mold foamed body was evaluated, and it was found that there was no concave-convex on its surface and there was basically no gap between the particles. The obtained in-mold foamed body was broken and its cross section was observed. The particles fully fused with other particles accounted for more than 60%, proving that its fusion rate was excellent.

[0161] The obtained in-mold foamed product was tested and evaluated for its density, flame retardancy level and oxygen index. The results are shown in Table 1.

[0162] <Comparative Examples 8 and 9>

[0163] [Preparation of polypropylene resin particles]

[0164] 100 parts by weight of a propylene-ethylene random copolymer (ethylene content: 2.2% by weight, MFR: 8.0 g / 10 minutes) was mixed with parts by weight of a sterically hindered amine ether flame retardant compound (NOR116FF) of a compound represented by the general formula (1) of the present invention, ammonium polyphosphate (APP for short), carbon black and talc as shown in Table 1 below, and the obtained mixture was kneaded using a twin-screw extruder with an extrusion setting temperature of up to 200° C. to obtain polypropylene resin pellets. The average particle weight of the polypropylene resin pellets was 1.0 mg.

[0165] [Preparation of polypropylene resin foamed particles]

[0166] By the same method as in the above example, polypropylene resin foamed particles were obtained, and the foaming ratio thereof was tested. The results are shown in Table 1.

[0167] [Preparation of in-mold foamed body]

[0168] By the same method as in the previous embodiment, a polyolefin resin in-mold foaming molding is obtained. Regarding the obtained in-mold foaming molding, the surface appearance and fusion rate meet the requirements, and the molding density, flame retardant grade and oxygen index are further tested and evaluated. The results are shown in Table 1.

[0169] Evaluations in Examples and Comparative Examples were performed as follows.

[0170] (Foaming ratio)

[0171] Calculate the weight W (g) and ethanol submerged volume V (cm 3), the density d (g / cm 3 ) is obtained by the following formula.

[0172] Foaming ratio = d × V / W

[0173] (Density of in-mold foamed body)

[0174] The apparent density MD (g / L) of the in-mold foamed body is calculated by dividing the weight W2 (g) of the foamed body by the volume V2 (L) of the foamed body: MD = W2 / V2

[0175] (Flame retardant grade)

[0176] The measurement and evaluation were performed in accordance with UL94 "Horizontal Burning Foaming Material Test", and the evaluation was performed according to the following standards.

[0177] ◎: HF-1 passed

[0178] ○: HF-2 passed

[0179] ×:HF NG

[0180] (Oxygen Index)

[0181] According to the provisions of GB / T 2406.2-2009, during the measurement, the in-mold foamed body is peeled and cut into 15 to 30 specimens of 80 to 150 mm × 10 mm × 10 mm. After conditioning at 23°C and 50% RH for at least 88 hours, the oxygen index is measured and the final result is calculated according to the lifting and lowering method.

[0182] According to Table 1, it can be seen that Comparative Example 1 cannot pass the HF-1 test due to the low content of aluminum hypophosphite. Although Comparative Examples 2 and 3 pass the HF-1 test, the aluminum hypophosphite does not meet the minimum requirements of the present invention, and the oxygen index is low. Compared with Comparative Example 1, although the compound represented by the general formula (1) of the present invention is added to Comparative Example 4, it still cannot reach the HF-1 level, and the oxygen index is even reduced. Comparative Examples 5-7 do not add MHB, and Comparative Example 5 cannot reach the HF-1 level, and the oxygen index is also low. Although Comparative Examples 6 and Comparative Examples 7 reach the HF-1 level, the oxygen index does not reach 27%. Comparative Examples 8 and 9 use ammonium polyphosphate flame retardant and the compound represented by the general formula (1) to match. Although a flat-plate molded body with a surface appearance and fusion rate that meet the requirements is obtained, it cannot pass the horizontal combustion foaming material test of UF94. It can be seen from Examples 1 to 14 that only by using the flame retardant composition mixed in the specific ratio specified in the present invention can a polyolefin resin in-mold foaming molding having HF-1 flame retardancy grade and high oxygen index while ensuring moldability be obtained.

[0183] Table 1

[0184]

[0185]

Claims

1. A polyolefin resin foamed particle, characterized in that: The invention comprises a polyolefin resin, an inorganic hypophosphite and a melamine flame retardant. Relative to 100 parts by weight of the polyolefin resin, the content of the inorganic hypophosphite is 1.8 to 4.0 parts by weight, and the content of the melamine flame retardant is 0.08 to 1.00 parts by weight. The melamine flame retardant is melamine hydrogen bromide. The foaming ratio of the polyolefin resin foamed particles is 5 to 45 times, The in-mold foamed body formed by molding the polyolefin resin foamed particles reaches UL94HF-1 grade and has an oxygen index of 27.0% or more.

2. The polyolefin resin foamed particles according to claim 1, characterized in that: The polyolefin resin foamed particles further include a compound represented by the general formula (1), R 1 NHCH2CH2CH2NR 2 CH2CH2NR 3 CH2CH2CH2NHR 4 (1) In the general formula (1), R 1 , R 2 is a group represented by the general formula (2), the dotted line above the triazine ring represented by the general formula (2) represents the connecting portion with the nitrogen atom in the general formula (1), R 3 and R 4 One of them is a group represented by the general formula (2), the dotted line above the triazine ring represented by the general formula (2) represents the connection part with the nitrogen atom in the general formula (1), R 3 and R 4 The other side is a hydrogen atom. In the general formula (2), R 5 is an alkyl group having 1 to 12 carbon atoms, R 6 is methyl, cyclohexyl or octyl, The content of the compound represented by the general formula (1) is 0.01 to 2.0 parts by weight based on 100 parts by weight of the polyolefin resin.

3. The polyolefin resin foamed particles according to claim 1 or 2, characterized in that: The polyolefin resin foamed particles further include one or more brominated flame retardants selected from brominated bisphenol A flame retardants, brominated bisphenol S flame retardants, brominated butadiene-styrene block copolymer flame retardants, and brominated polyphenylene ether flame retardants.

4. The polyolefin resin foamed particles according to claim 3, characterized in that: The brominated flame retardant includes at least one of brominated bisphenol A flame retardant and brominated bisphenol S flame retardant. The content of the brominated flame retardant is 0.1 to 5.0 parts by weight relative to 100 parts by weight of the polyolefin resin.

5. The polyolefin resin foamed particles according to claim 1 or 2, characterized in that: The polyolefin resin foamed particles further include a free radical initiator.

6. The polyolefin resin foamed particles according to claim 5, characterized in that: The free radical initiator includes at least one of 2,3-dimethyl-2,3-diphenylbutane and poly-1,4-diisopropylbenzene, and the content of the free radical initiator is 0.01 to 0.5 parts by weight relative to 100 parts by weight of the polyolefin resin.

7. The polyolefin resin foamed particles according to claim 1 or 2, characterized in that: The polyolefin resin is a polypropylene resin.

8. A method for preparing polyolefin resin foamed particles, characterized in that: The method comprises dispersing polyolefin resin particles in an aqueous dispersion medium in a sealed container, heating the mixture to a temperature above the softening temperature of the polyolefin resin particles in the presence of a foaming agent, and then releasing the obtained mixture into an environment with a pressure lower than the internal pressure of the sealed container to foam the polyolefin resin particles to obtain the polyolefin resin foamed particles; The polyolefin resin particles include polyolefin resin, inorganic hypophosphite and melamine flame retardant. Relative to 100 parts by weight of the polyolefin resin, the content of the inorganic hypophosphite is 1.8 to 4.0 parts by weight, and the content of the melamine flame retardant is 0.08 to 1.00 parts by weight. The melamine flame retardant is melamine hydrogen bromide. The foaming ratio of the polyolefin resin foamed particles is 5 to 45 times, The in-mold foamed body formed by molding the polyolefin resin foamed particles reaches UL94HF-1 grade and has an oxygen index of 27.0% or more.

9. A polyolefin resin foamed molded body, characterized in that: The foamed polyolefin resin particles are obtained by subjecting the foamed polyolefin resin particles according to any one of claims 1 to 7 or the foamed polyolefin resin particles obtained by the preparation method according to claim 8 to in-mold foaming.

10. The polyolefin resin foamed molded article according to claim 9, wherein The polyolefin resin foamed molded body reaches UL94 HF-1 grade, and the oxygen index is not less than 27%. 11 . An interior material for public transportation, comprising the polyolefin resin foamed molded article according to claim 9 or 10.

Images