Flame-retardant resin composition as well as preparation method and application thereof

Abstract

The invention relates to the field of plastic processing, in particular to a halogen-free flame-retardant resin composition as well as a preparation method and application thereof. The flame-retardant resin composition contains a base resin, a modified vinyl alcohol resin and an optional auxiliary agent, a polymer in the modified vinyl alcohol resin comprises a polymer main chain and a modified group grafted on the polymer main chain; the polymer main chain is derived from an ethylene-vinyl alcohol copolymer and a derivative thereof; the modified group comprises a phosphorus element-containing group and a hydrophobic alkyl group. The flame-retardant resin composition not only has a good flame-retardant effect, but also has better gas barrier property, has good affinity with common base resin, is suitable for being prepared into a multilayer film, and is particularly suitable for preparing compositions and products in the fields of food packaging, electronic element packaging, container linings and the like.

Description

Technical Field

[0001] This invention relates to the field of plastics processing, and more specifically, to a flame-retardant resin composition, its preparation method, and its application. Background Technology

[0002] Polymer materials are widely used in parts encapsulation, product packaging, and surface treatment due to their excellent acid and alkali resistance, flexibility, light weight, and simple molding processes. With the continuous advancement of science and technology, human production activities are becoming increasingly diversified, and life is becoming richer, leading to more complex application scenarios for related materials. Consequently, people are placing higher demands on the comprehensive performance of materials. The inherent flammability of polymer products makes them difficult to meet fire safety requirements in applications. Furthermore, the high barrier properties commonly used in encapsulation, packaging, or coating are relatively expensive, all of which limit the application of polymer materials in fields such as home appliances and automobiles.

[0003] To minimize and reduce fires caused by the combustion of polymer materials, many countries have formulated and improved relevant laws, regulations, and industry standards, mandating that polymer materials used in these applications must possess highly efficient flame-retardant properties. Polymer materials are primarily composed of carbon and hydrogen, making them prone to violent combustion in the presence of accelerants, leading to fires and other safety accidents. Therefore, endowing plastics with flame-retardant properties broadens their application range and meets people's demands for fire safety performance. Currently, flame retardants used for polymer materials mainly include halogenated flame retardants, inorganic flame retardants, and intumescent flame retardants. Halogenated flame retardants have high flame-retardant efficiency for polymer materials, but due to their serious safety and environmental hazards, their application in large quantities is increasingly limited. Inorganic flame retardants, such as magnesium hydroxide and aluminum hydroxide, while environmentally friendly, have low flame-retardant efficiency, requiring high dosages to achieve a certain flame-retardant effect. Furthermore, these flame retardants have poor dispersibility, significantly impacting the mechanical and barrier properties of the substrate, and are not suitable for use alone. Intumescent flame retardants have advantages such as high flame retardant efficiency, low smoke, and low toxicity. By compounding small amounts of halogenated, phosphorus, and nitrogen-based flame retardants, the flame retardant efficiency can be synergistically improved. This has been recognized as one of the effective ways to achieve low-halogen or halogen-free flame retardants.

[0004] Currently, additives used to improve the barrier properties of materials mainly include sheet-like nanoparticles, sheet-like inorganic materials, or ethylene-vinyl alcohol copolymers. These additives are distributed in a layered structure within the material, thereby extending the medium's passage path and reducing its permeability, thus improving barrier properties. However, sheet-like nanoparticles and sheet-like inorganic materials are relatively expensive, and their interfacial compatibility with the resin matrix is ​​poor, leading to poor dispersibility and potentially negatively impacting the material's mechanical properties. Polymers such as ethylene-vinyl alcohol copolymers, on the other hand, have relatively low raw material costs and good barrier effects, making them a more ideal barrier modifier. However, the addition of these polymers dilutes flame retardants, thus worsening the flame retardant effect of the material. Similarly, the addition of flame retardants alters the viscosity of the matrix resin, affecting the blending effect of the barrier polymer within the matrix resin and consequently impacting the material's barrier properties.

[0005] Therefore, how to avoid the problems of easy migration and poor compatibility with the substrate caused by added flame retardants, and how to provide a modified vinyl alcohol resin that has good flame retardant effect, good gas barrier properties and good affinity with the substrate, so as to combine it with ordinary resin to obtain a flame retardant resin composition that is flame retardant, has good gas barrier properties and is suitable for preparing multilayer films, is a technical problem that needs to be solved. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention proposes a flame-retardant resin composition with barrier properties, specifically relating to a flame-retardant resin composition with barrier properties, its preparation method, and its applications. This flame-retardant resin composition possesses both excellent flame-retardant effects and good gas barrier properties, and exhibits good compatibility with ordinary resins, making it suitable for preparing multilayer films. It is particularly suitable for the preparation of compositions and articles in the fields of food packaging, electronic component encapsulation, and container linings.

[0007] A first aspect of the present invention is to provide a flame-retardant resin composition comprising a base resin, a modified vinyl alcohol resin, and optional additives; said modified vinyl alcohol resin comprising a polymer backbone and modifying groups grafted onto said polymer backbone;

[0008] The polymer backbone is derived from polymer raw materials comprising the following polymers and / or derivatives thereof: ethylene-vinyl alcohol copolymer;

[0009] The modified groups include phosphorus-containing groups and hydrophobic hydrocarbon groups, wherein the hydrophobic hydrocarbon groups contain more than 4 carbon atoms;

[0010] The phosphorus-containing group is derived from modified compound one, which is selected from at least one of inorganic phosphoric acid and its derivatives, and organic phosphoric acid and its derivatives.

[0011] The flame-retardant resin composition of this invention uses a modified vinyl alcohol resin. This modified vinyl alcohol resin not only exhibits higher flame retardancy than unmodified vinyl alcohol resin, but the non-polar nature of its molecular chains also significantly improves its affinity with other non-polar resin components. This addresses the problems of poor interfacial interaction and weak flame retardancy faced by vinyl alcohol barrier resins during use. The flame-retardant resin composition of this invention not only retains the barrier properties of the original vinyl alcohol resin but also possesses excellent flame-retardant effects. When prepared into a multilayer film, the interlayers exhibit good affinity and stronger interlayer bonding.

[0012] The modifying groups are linked to the polymer backbone through hydroxyl groups in the polymer raw material. According to some preferred embodiments of the present invention, in the modified vinyl alcohol resin: the modification rate of the phosphorus-containing groups on the polymer raw material is 0-85 mol%, and not 0, preferably 10-30 mol%, based on the content of all hydroxyl groups in the polymer raw material being 100 mol%. The degree of modification of the vinyl alcohol resin within the above-mentioned preferred range allows it to still possess crystalline vinyl alcohol blocks with hydrogen bonds, maintaining its good gas barrier properties while improving flame retardant and hydrophobic properties.

[0013] According to some preferred embodiments of the present invention, the phosphorus-containing group is connected to the polymer backbone via one or more ester bonds.

[0014] According to some preferred embodiments of the present invention, the molar ratio of the hydrophobic hydrocarbon group to phosphorus is 1:(1-3), for example, it can be 1 to 1, 1.3, 1.5, 1.8, 2, 2.3, 2.5, 2.8, 3, or any two values ​​or any range of any two values. Preferably, it is 1:(1.3-1.9).

[0015] According to some preferred embodiments of the present invention, the hydrophobic hydrocarbon group is selected from chain hydrocarbon groups and / or cyclic hydrocarbon groups containing 4 or more carbon atoms, more preferably from chain hydrocarbon groups and / or cyclic hydrocarbon groups containing 4 to 18 carbon atoms, such as chain hydrocarbon groups and / or cyclic hydrocarbon groups containing 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and 18 carbon atoms. The chain hydrocarbon group includes, but is not limited to, chain alkyl groups, and the cyclic hydrocarbon group includes, but is not limited to, cycloalkyl and aryl groups. The term "chain hydrocarbon group and cyclic hydrocarbon group containing 4 to 18 carbon atoms" means that the group simultaneously contains both chain hydrocarbon groups and cyclic hydrocarbon groups, and the total number of carbon atoms in the chain hydrocarbon group and cyclic hydrocarbon group is 4 to 18 carbon atoms.

[0016] As mentioned above, the phosphorus-containing group is derived from modified compound one, which is selected from at least one of inorganic phosphoric acid and its derivatives, organic phosphoric acid and its derivatives. For example, modified compound one may be one or more of phosphoric acid compounds, organic phosphoric acid compounds, phosphate ester compounds, organic phosphate ester compounds, phosphoramide compounds, phosphate compounds, and organic phosphate compounds.

[0017] According to some preferred embodiments of the present invention, the modified compound is selected from at least one of halogen-containing inorganic phosphoric acid derivatives and halogen-containing organic phosphoric acid derivatives. Preferably, the halogen is selected from one or more of fluorine, chlorine, bromine, and iodine. More preferably, the modified compound is selected from one or more of phosphorus oxychloride, pyrophosphoryl chloride, dicyclohexylphosphoryl chloride, bis(dimethylamino)chlorate phosphorus, phenylphosphoryl dichloride, diphenylphosphine chloride, diethylphosphite chloride, and O,O-dimethylphosphoryl chloride.

[0018] According to some preferred embodiments of the present invention, the hydrophobic hydrocarbon group is connected to the phosphorus-containing group through an ester bond, amide bond, or secondary valence bond, and / or the hydrophobic hydrocarbon group originates from the hydrophobic hydrocarbon group itself contained in the phosphorus-containing group; that is, when the first modified compound contains a hydrophobic hydrocarbon group, the hydrophobic hydrocarbon group originates from the hydrophobic hydrocarbon group itself contained in the first modified compound; when the first modified compound does not contain a hydrophobic hydrocarbon group, the hydrophobic hydrocarbon group originates from an external compound capable of reacting with the phosphorus-containing group in the first modified compound; more preferably, when the first modified compound does not contain a hydrophobic hydrocarbon group, the hydrophobic hydrocarbon group is derived from a second modified compound capable of reacting with an acyl chloride or an acid; preferably, the second modified compound is selected from at least one of organic amines, organic alcohols, and acyl chlorides containing the hydrophobic hydrocarbon group, more preferably, the second modified compound is selected from at least one of n-hexylamine, cyclohexylamine, dodecyl alcohol, and dodecyl chloride, and more preferably, organic amines. When the modified compound is selected from organic amines, it has superior flame retardant properties due to the introduction of nitrogen.

[0019] Based on the above selection of raw materials and reaction principle, it can be seen that although some of the modified compounds that provide modifying groups for the modified vinyl alcohol resin in this invention involve halogens, such as acyl chlorides, the role of the halogens is to provide reaction sites for the modified compounds. After the reaction, the halogens will not exist on the modified vinyl alcohol resin. Therefore, the modified vinyl alcohol resin in this invention is a halogen-free flame retardant.

[0020] In this invention, the hydrophobic group containing four or more carbon hydrocarbon groups can be derived from a modified compound II containing four or more carbon hydrocarbon groups that can react with acyl chlorides or acids, such as one or more of n-hexylamine, cyclohexylamine, dodecyl alcohol, ethanolamine, and dodecyl chloride; or it can be derived from a phosphoric acid raw material containing hydrophobic groups, i.e., modified compound I, such as dicyclohexylphosphochloride, phenylphosphodichloride, and diphenylphosphine chloride. For example, when one or more of dicyclohexylphosphochloride, phenylphosphodichloride, and diphenylphosphine chloride are used as modified compound I, it contains hydrophobic groups such as cyclohexyl and phenyl. In this case, the hydrophobic hydrocarbon group can be derived from the above groups contained in such modified compound I itself. In the preparation method, only one grafting reaction is required.

[0021] According to the present invention, the polymer raw material is a blend formed from one or more commercial ethylene-vinyl alcohol copolymers and / or their derivatives.

[0022] According to some preferred embodiments of the present invention, the number average molecular weight of the ethylene-vinyl alcohol copolymer is between 10,000 and 200,000, for example, 10,000, 50,000, 100,000, 150,000, 200,000, and any two values ​​or any range of any two values, and / or, the melt index measured at 190°C and 2.16 kg is between 0.5 and 25 g / 10 min, for example, 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, and any two values ​​or any range of any two values, and / or, the structural units derived from ethylene monomer account for 15% to 50%, for example, 15%, 20%, 30%, 40%, 50%, and any two values ​​or any range of any two values, based on the total molar amount of all structural units.

[0023] According to some preferred embodiments of the present invention, the phosphorus content in the modified vinyl alcohol resin is 2 to 30 wt%, for example 2 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, and any two values ​​or any range of any two values, preferably 3 to 18 wt%, with the total mass of the modified vinyl alcohol resin being 100 wt%.

[0024] According to some preferred embodiments of the present invention, a test sample of the modified vinyl alcohol resin material is prepared according to the contents described in section "7 Specimen" of GB / T 30693-2014. The test sample of the modified vinyl alcohol resin material is tested according to the test method described in section "10 Experimental Procedure" of GB / T 30693-2014. The water contact angle of the test sample of the modified vinyl alcohol resin material is not less than 100°, preferably 110-140°.

[0025] According to some preferred embodiments of the present invention, the second test sample of the modified vinyl alcohol resin material is prepared according to the contents described in section "7 Sample Preparation" of GB / T 2406.2-2009, and the second test sample of the modified vinyl alcohol resin material is tested according to the detection method described in section "8 Procedure for Determining Oxygen Index" of GB / T 2406.2-2009, and the limiting oxygen index of the second test sample of the modified vinyl alcohol resin material is not less than 22%.

[0026] According to a preferred embodiment of the present invention, the modified vinyl alcohol resin of the present invention is prepared by the following method, which includes:

[0027] In the presence of an acid-binding agent, the polymer raw material is grafted with the modified compound in a solvent, wherein the modified compound is selected from at least one of inorganic phosphoric acid and its derivatives, and organic phosphoric acid and its derivatives.

[0028] When the modified compound one contains the hydrophobic hydrocarbon group, the modified vinyl alcohol resin is obtained after the grafting reaction one; or,

[0029] When the modified compound one does not contain the hydrophobic hydrocarbon group, after the first grafting reaction, the modified compound two containing the hydrophobic hydrocarbon group is further subjected to a second grafting reaction to obtain the modified vinyl alcohol resin.

[0030] The polymer raw material comprises ethylene-vinyl alcohol copolymer and / or its derivatives.

[0031] As an example, specifically, the following steps may be included:

[0032] (1) Dissolve, swell or disperse the polymer raw material in an organic solvent, and add a modified compound to carry out a grafting reaction.

[0033] (2) Depending on the condition of modified compound one, modified compound two may be added to the product obtained in step (1) to carry out grafting reaction two to obtain the final product.

[0034] According to some preferred embodiments of the present invention, the modified compound is selected from at least one of halogen-containing inorganic phosphoric acid derivatives and halogen-containing organic phosphoric acid derivatives. Preferably, the halogen is selected from one or more of fluorine, chlorine, bromine, and iodine. More preferably, the modified compound is selected from one or more of phosphorus oxychloride, pyrophosphoryl chloride, dicyclohexylphosphoryl chloride, bis(dimethylamino)chlorate phosphorus, phenylphosphoryl dichloride, diphenylphosphine chloride, diethylphosphite chloride, and O,O-dimethylphosphoryl chloride. Thus, in the first step, the hydroxyl groups in the polymer raw material form ester bonds with the modified compound, such as phosphoric acid or phosphoryl chloride.

[0035] According to some preferred embodiments of the present invention, the modified compound 2 is selected from compounds that can react with acyl chlorides or acids and contain a hydrophobic hydrocarbon group with 4 or more carbon atoms, such that the hydrophobic group is combined with the remaining group on the phosphate; preferably, the modified compound 2 is selected from at least one of organic amines, organic alcohols, and acyl chlorides containing the hydrophobic hydrocarbon group, and the hydrophobic hydrocarbon group is connected to the phosphorus-containing group through ester bond, amide bond or secondary valence bond force.

[0036] More preferably, the hydrophobic hydrocarbon group is selected from chain hydrocarbon groups and / or cyclic hydrocarbon groups containing 4 or more carbon atoms, and more preferably from chain hydrocarbon groups and / or cyclic hydrocarbon groups containing 4 to 18 carbon atoms, such as one or more of straight-chain alkyl, alkyl-substituted, and aromatic groups;

[0037] More preferably, the modified compound is selected from at least one of n-hexylamine, cyclohexylamine, dodecyl alcohol, and dodecyl chloride.

[0038] According to some preferred embodiments of the present invention, the amount of the modified compound one is 10 to 500 parts by weight relative to 100 parts of polymer raw material, for example, 10 parts, 50 parts, 100 parts, 200 parts, 300 parts, 400 parts, 500 parts, and any two values ​​or any range of any two values, preferably 40 to 200 parts.

[0039] According to some preferred embodiments of the present invention, the molar ratio of modified compound one to modified compound two is 1:(0 to 4). Preferably, when modified compound two is added, the molar ratio of modified compound one to modified compound two is 1:(1 to 4), for example, 1 to 1, 2, 3, 4, and any two values ​​or any range of any two values.

[0040] The acid-binding agent can be a common acid-binding agent in the art. According to some preferred embodiments of the present invention, the acid-binding agent is selected from at least one of organic bases or weak acid compounds; more preferably, it is an acid-binding agent that provides catalysis and removal of by-products for acyl chloride grafting reaction, preferably at least one of triethylamine, potassium carbonate, and sodium carbonate.

[0041] The organic solvent may be the modified compound itself, or one or more aprotic solvents, including but not limited to: dichloromethane, chloroform, acetonitrile, n-hexane, cyclohexane, and p-dimethyl sulfoxide. According to some preferred embodiments of the present invention, the solvent is selected from one or more of dichloromethane, acetonitrile, n-hexane, cyclohexane, and p-dimethyl sulfoxide.

[0042] According to some preferred embodiments of the present invention, the amount of solvent used is 500 to 10,000 parts by weight relative to 100 parts of polymer raw material.

[0043] According to some preferred embodiments of the present invention, the molar ratio of the modified compound one to the acid-binding agent is 1:(0.5-3), preferably 1:(1-3), for example, the ratio of 1 to 1, 2, 3, or any two values ​​or any range of any two values.

[0044] The reaction conditions for the first grafting reaction are conventional conditions, as long as the modified compound is grafted onto the polymer raw material. According to some preferred embodiments of the present invention, the conditions for the first grafting reaction include: being carried out under a protective atmosphere, preferably selected from nitrogen and / or an inert gas; and / or, a temperature of (-10)℃ to 90℃; and / or, a time of 0.1 to 48h.

[0045] Preferably, the reaction temperature is (-10) to 30°C, and / or the reaction time is 3 to 15 h.

[0046] According to some preferred embodiments of the present invention, the conditions for the second grafting reaction include:

[0047] The reaction is carried out under a protective atmosphere, preferably selected from nitrogen and / or an inert gas; and / or, at a temperature of (-10)℃ to 110℃; and / or, for a reaction time of 0.1 to 48 h; preferably,

[0048] The modified compound 2 is directly mixed with the product mixture obtained from the first grafting reaction, and the second grafting reaction is carried out in the mixture system obtained from the first grafting reaction (i.e., one-pot method). Alternatively, the modified product obtained from the first grafting reaction is first separated from the product mixture system obtained from the first grafting reaction, and then the modified product obtained from the first grafting reaction is grafted with the modified compound 2.

[0049] More preferably, when grafting reaction two is carried out in a mixed system containing the product obtained from grafting reaction one, the reaction temperature is (-10)℃~30℃, and / or the reaction time is 3~15h; when the modified product obtained from grafting reaction one is first separated from the mixed system of products obtained from grafting reaction one, and then the modified product obtained from grafting reaction one is grafted with modified compound two, the reaction temperature is 50~110℃, and / or the reaction time is 3~15h.

[0050] Preferably, the second grafting reaction is carried out under mixed conditions.

[0051] According to the present invention, in the case of grafting reaction two, the product (suspension) obtained from grafting reaction one can be directly subjected to grafting reaction two (i.e., a one-pot method), or the product (suspension) obtained from grafting reaction one can be post-treated (separated, washed, and dried) before grafting reaction two, that is, the dried product can be directly added to modified compound two (i.e., modified compound two also acts as a solvent) or a solution containing modified compound two for reaction. Preferably, a one-pot method is used for stepwise reaction, which saves reaction steps. Furthermore, the inventors of the present invention have found that the modified polymer obtained by the one-pot method has superior flame retardant and hydrophobic properties.

[0052] The washing can be performed using a conventional washing solvent, such as at least one selected from n-hexane, isohexane, cyclohexane, n-heptane, n-octane, isooctane, diethyl ether, isopropyl ether, and methyl tert-butyl ether. The concentration of the solution containing modified compound II can be 0.5–50 wt%, preferably 10–50 wt%. The solvent used for the solution containing modified compound II can be the same solvent used in grafting reaction I, which is not required by this invention.

[0053] The base resin in this invention can be selected from a wide range. Preferably, the base resin is one or more thermoplastic resins; more preferably, the base resin is selected from one or more of the following resins and their derivatives: polyolefins, polyoxymethylene, nylon, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, polycarbonate, polyphenylene ether, polyphenylene sulfide, epoxy resin, unsaturated polyester, and vinyl resin.

[0054] The flame-retardant resin composition of this invention may or may not contain additives. These additives are raw materials selectively added during resin molding to improve its processing performance or address inherent resin deficiencies. They include, but are not limited to, one or more of antioxidants, anti-aging agents, release agents, fillers, colorants, heat stabilizers, antibacterial agents, lubricants, plasticizers, and antistatic agents. The specific dosages are also conventional in the art, and those skilled in the art can select them according to convention. For example, by weight: relative to 100 parts of base resin, the amount of antioxidant is 0-5 parts, preferably 0-1 parts; and / or, relative to 100 parts of base resin, the amount of anti-aging agent is 0-5 parts, preferably 0-2 parts; and / or, relative to 100 parts of base resin, the amount of filler is 0-300 parts, preferably 0-50 parts; and / or, relative to 100 parts of base resin, the amount of colorant is 0-2 parts, preferably 0-0.5 parts; and / or, relative to 100 parts of base resin, the amount of colorant is... The amount of the heat stabilizer is 0-5 parts, preferably 0-2 parts; and / or, relative to 100 parts of the base resin, the amount of the antibacterial agent is 0-10 parts, preferably 0-5 parts; and / or, relative to 100 parts of the base resin, the amount of the lubricant is 0-5 parts, preferably 0-3 parts; and / or, relative to 100 parts of the base resin, the amount of the plasticizer is 0-100 parts, preferably 0-50 parts; and / or, relative to 100 parts of the base resin, the amount of the antistatic agent is 0-5 parts, preferably 0-3 parts.

[0055] In this invention, the ratio of base resin to modified vinyl alcohol resin can be selected within a wide range. Preferably, by weight, the content of modified vinyl alcohol resin is 50 to 400 parts relative to 100 parts of base resin, and more preferably 150 to 250 parts.

[0056] A second aspect of the present invention is to provide a method for preparing the flame-retardant resin composition described in the first aspect, comprising mixing raw materials including the base resin, the modified vinyl alcohol resin and optional additives, and melt extruding.

[0057] In this invention, the mixing conditions are conventional conditions in the field of plastics processing.

[0058] In this invention, the melt extrusion conditions of the flame-retardant resin composition are conventional processing conditions in the field of plastics processing. Those skilled in the art can select appropriate extrusion conditions based on the resin raw materials, for example, the processing conditions in the examples can be used. This is a conventional choice in the art and is not specifically limited here. For example, the melt extrusion temperature is 190-260°C.

[0059] A third aspect of the present invention is to provide a single-layer sheet, wherein the single-layer sheet is made of the flame-retardant resin composition described in the first aspect or the flame-retardant resin composition obtained by the preparation method described in the second aspect;

[0060] Preferably, the single-layer sheet is a single-layer film.

[0061] The methods for preparing single-layer sheets or single-layer films are conventional methods in the art, including but not limited to the methods in the embodiments of the present invention.

[0062] A fourth aspect of the present invention is to provide a multilayer composite sheet, wherein the raw material of the multilayer composite sheet is the flame-retardant resin composition described in the first aspect;

[0063] The base resin and the modified vinyl alcohol resin are respectively located in different sheet layers of the multilayer sheet, the multilayer sheet including sheet layer A formed containing the base resin and optional additives; the multilayer sheet also includes sheet layer B formed containing the modified vinyl alcohol resin and optional additives.

[0064] In this invention, the compositions for sheet layer A and sheet layer B may each contain additives or not. The additives are raw materials selected and added during the molding process of the resin to improve its processing performance or to compensate for the shortcomings of the resin itself. These additives include, but are not limited to, one or more of antioxidants, anti-aging agents, release agents, fillers, colorants, heat stabilizers, antibacterial agents, lubricants, plasticizers, and antistatic agents. The specific dosages are also conventional dosages in the art, and those skilled in the art can select them according to convention.

[0065] In this invention, when preparing multilayer sheets, the specific amounts of additives contained in the composition for sheet layer A and the composition for sheet layer B are also conventional amounts in the art, and those skilled in the art can select them according to convention. For example, relative to the resin raw material in each sheet layer, for example, the resin raw material in sheet layer A is a base resin, and the resin in sheet layer B is a modified vinyl alcohol resin, based on parts by weight, with the content of resin raw material in each sheet layer being 100 parts, the content of antioxidant is 0-5 parts, preferably 0-1 parts; and / or, the content of anti-aging agent is 0-5 parts, preferably 0-2 parts; and / or, the content of release agent is 0-5 parts, preferably 0-2 parts; and / or The filler is 0-300 parts, preferably 0-50 parts; and / or, the colorant is 0-2 parts, preferably 0-0.5 parts; and / or, the heat stabilizer is 0-5 parts, preferably 0-2 parts; and / or, the antibacterial agent is 0-10 parts, preferably 0-5 parts; and / or, the lubricant is 0-5 parts, preferably 0-3 parts; and / or, the plasticizer is 0-100 parts, preferably 0-50 parts; and / or, the antistatic agent is 0-5 parts, preferably 0-3 parts.

[0066] Preferably, the multilayer sheet is a multilayer film.

[0067] Preferably, the multilayer sheet is a three-layer sheet, with sheet layer B located in the middle of the three layers and having an ABA structure; more preferably,

[0068] Based on weight, the content of the modified vinyl alcohol resin is 50 to 400 parts, preferably 150 to 250 parts, relative to 100 parts of the base resin in the three-layer sheet; more preferably, the content of the base resin in the two sheet layers A is equal.

[0069] A fifth aspect of the present invention is to provide a method for preparing the multilayer composite sheet described in the fourth aspect, comprising:

[0070] Raw materials containing a base resin and optional additives are mixed and melt-extruded to obtain a composition for sheet layer A;

[0071] Raw materials containing modified vinyl alcohol resin and optional additives are mixed and melt-extruded to obtain a composition for sheet layer B.

[0072] The composition for sheet layer A and the composition for sheet layer B are co-extruded according to the structure of a multilayer sheet to obtain the multilayer sheet; optionally, the multilayer sheet is prepared into a film to obtain a multilayer film.

[0073] In this invention, the melt extrusion conditions for preparing the composition for sheet layer A and the composition for preparing sheet layer B are both conventional processing conditions in the field of plastics processing. Those skilled in the art can select appropriate extrusion conditions based on the resin raw materials; for example, the processing conditions shown in the examples can be used. This is a conventional choice in the field and is not specifically limited here. For example, the melt extrusion temperature is 190-260°C.

[0074] In this invention, the co-extrusion conditions used in preparing multilayer sheets are also conventional processing conditions in the field of plastics processing. Those skilled in the art can select appropriate extrusion conditions based on the resin raw materials, for example, the processing conditions shown in the examples can be used. This is a conventional choice in the field and is not specifically limited herein.

[0075] According to the present invention, the thickness of the composite film has a wide range of selection, and those skilled in the art can adjust it according to actual applications. The present invention does not make specific requirements.

[0076] The sixth aspect of the present invention is to provide the application of the flame-retardant resin composition described above, or the single-layer sheet or the multi-layer composite sheet described above, preferably in the fields of encapsulation and lining, in food packaging, electronic component encapsulation, and container lining.

[0077] The flame-retardant resin composition of this invention uses a modified vinyl alcohol resin, retaining the barrier properties of the original vinyl alcohol resin. Simultaneously, the flame-retardant groups of the modified ethylene-vinyl alcohol copolymer are chemically bonded to the molecular chain, effectively avoiding problems such as easy migration and poor compatibility with the substrate caused by added flame retardants. This modified vinyl alcohol resin not only has higher flame retardancy than unmodified vinyl alcohol resin, but the non-polar nature of the resin molecular chain also significantly improves its affinity with other non-polar resin components, thus addressing the problems of poor interfacial interaction and poor flame retardancy faced by vinyl alcohol barrier resins during use.

[0078] In summary, the flame-retardant resin composition of the present invention not only retains the barrier properties of the original vinyl alcohol resin, but also has a good flame-retardant effect. When the flame-retardant resin composition exists in the form of a multilayer film, the interlayers in the multilayer film have good affinity and stronger interlayer bonding. Detailed Implementation

[0079] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0080] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0081] Raw material source:

[0082] Ethylene-vinyl alcohol copolymer (EVOH): Grade EVOH H171B, Kuraray, Japan;

[0083] Phosphorus oxychloride: Shandong Maofa Chemical Co., Ltd.

[0084] Dichloromethane: Jinan Qichen Chemical Co., Ltd.

[0085] Dodecanol: Guangzhou Baosheng Chemical Co., Ltd.

[0086] Triethylamine: Shandong Zhouhe Chemical Co., Ltd.

[0087] Dodecyl chloride: Shandong Duolian Chemical Co., Ltd.

[0088] Polyethylene (PE): Grade 7042, Maoming Petrochemical;

[0089] Polypropylene (PP): Cangzhou Refining & Chemical GD-H-230;

[0090] Nylon 66 (PA66): Rhodia A205F;

[0091] Polyethylene terephthalate (PET): DuPont 415HPNC;

[0092] Ethylene-vinyl acetate copolymer (EVA): ExxonMobil EVA550;

[0093] Compound antioxidant: The antioxidant 1010 (BASF), antioxidant 168 (BASF), and calcium stearate (Shandong Haona) are mixed evenly in a mass ratio of 2 / 2 / 1.

[0094] In the following examples, the content of phosphorus-containing groups corresponds to the content of phosphorus element, and when organic amine is used as the modified compound 2, the content of hydrophobic groups corresponds to the content of nitrogen element groups. The content of phosphorus element groups and nitrogen element groups are both obtained by elemental analysis instrument (EA). When calculating the phosphorus element group modification rate, the content of hydroxyl groups in the raw materials before the reaction is 100 mol%.

[0095] The phosphorus content (wt%) of the final product was calculated by measuring the weight gain after the reaction and by using the results from an elemental analyzer (EA).

[0096] In the following examples, room temperature refers to 25°C.

[0097] Preparation of modified ethylene-vinyl alcohol copolymer:

[0098] Example A1:

[0099] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 500ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 90g of triethylamine was added, and then 45g of phosphorus oxychloride was added dropwise to the system under a dry nitrogen atmosphere. The reaction was carried out at low temperature for 12h.

[0100] (2) The system was placed in a water bath at room temperature and heated to room temperature. 220g of dodecanol was added under a dry nitrogen atmosphere and the reaction was carried out at room temperature for 6h.

[0101] (3) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product, namely the modified ethylene-vinyl alcohol copolymer.

[0102] Example A2

[0103] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 500ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 30g of triethylamine was added, and then 45g of phosphorus oxychloride was added dropwise to the system under a dry nitrogen atmosphere. The reaction was carried out at low temperature for 12h.

[0104] (2) The suspended matter in the system was filtered and separated, dried under dry conditions, and then added to 220g of dodecanol. The system was heated to 100℃ and reacted for 6h.

[0105] (3) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0106] Example A3:

[0107] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 500ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 40g of triethylamine was added to the system, and then 70g of diphenylphosphine chloride was added dropwise to the system under a dry nitrogen atmosphere. The system was reacted at low temperature for 12h.

[0108] (2) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0109] Example A4

[0110] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 500ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 30g of triethylamine was added, and then 45g of phosphorus oxychloride was added dropwise to the system under a dry nitrogen atmosphere. The reaction was carried out at low temperature for 12h.

[0111] (2) The suspended matter in the system was filtered and separated, dried under dry conditions, and then added to 120g of n-hexylamine. The system was heated to 100℃ and reacted for 6h.

[0112] (3) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0113] Example A5:

[0114] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 500ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 30g of triethylamine was added, and then 45g of phosphorus oxychloride was added dropwise to the system under a dry nitrogen atmosphere. The reaction was carried out at low temperature for 12h.

[0115] (2) The suspended matter in the system was filtered and separated, dried under dry conditions, and then added to 220g of dodecylamine. The system was heated to 100℃ and reacted for 6h.

[0116] (3) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0117] Example A6:

[0118] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 500ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 30g of triethylamine was added, and then 45g of phosphorus oxychloride was added dropwise to the system under a dry nitrogen atmosphere. The reaction was carried out at low temperature for 12h.

[0119] (2) The suspended matter in the system was filtered and separated, dried under dry conditions, and then added to 320g of octadecylamine. The system was heated to 100℃ and reacted for 6h.

[0120] (3) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0121] Comparative Example A1:

[0122] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 300ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃ and stirred at low temperature for 12h.

[0123] (2) The system was placed in a room temperature water bath and heated to room temperature. Under a dry nitrogen atmosphere, the system was stirred at room temperature for 6 hours.

[0124] (3) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0125] Comparative Example A2:

[0126] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 300ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 30g of triethylamine was added, and then 45g of phosphorus oxychloride was added dropwise to the system under a dry nitrogen atmosphere. The reaction was carried out at low temperature for 12h.

[0127] (2) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0128] Comparative Example A3:

[0129] (1) 100g of ethylene-vinyl alcohol copolymer was crushed and dispersed in 300ml of dry dichloromethane. The entire system was placed in an ice-water bath to keep the system temperature at around 0℃. 30g of triethylamine was added, and then 60g of dodecyl chloride was added dropwise to the system under a dry nitrogen atmosphere. The reaction was carried out at low temperature for 12h.

[0130] (2) The suspended matter in the system is filtered and separated, and washed three times with water to obtain the final product.

[0131] The formulations of the above examples and comparative examples are shown in Table 1. The properties of the products prepared in the examples and comparative examples are shown in Table 2.

[0132] Table 1

[0133]

[0134] The products in the examples and comparative examples were tested using the following methods, and the results are recorded in Table 2.

[0135] The limiting oxygen index is determined as follows: Test sample two of the modified vinyl alcohol resin material is prepared according to the contents described in "7 Sample Preparation" of GB / T 2406.2-2009, and the test sample two of the modified vinyl alcohol resin material is tested according to the test method described in "8 Procedure for Determining Oxygen Index" of GB / T 2406.2-2009.

[0136] The method for testing the water contact angle is as follows: a test sample of the modified vinyl alcohol resin material is prepared according to the contents described in "7 Samples" of GB / T 30693-2014, and the test sample of the modified vinyl alcohol resin material is tested according to the test method described in "10 Test Procedures" of GB / T 30693-2014.

[0137] Table 2

[0138]

[0139] The test results of Comparative Example A1 show that EVOH resin has a low limiting oxygen index, is highly flammable, and has a low water contact angle, indicating strong polarity and poor affinity with non-polar polyolefin resins.

[0140] By comparing Comparative Example A1 and Comparative Example A2, it can be seen that the addition of phosphorus-containing compounds can significantly improve the flame retardant properties of the material, but the surface polarity of the material is still very high, specifically manifested in the increase of limiting oxygen index while the water contact angle is still low. By comparing Comparative Example A1 and Comparative Example A3, it can be seen that attaching long chains obtained by hexanoyl chloride or dodecyl chloride to the molecular chain can improve the water contact angle of the material, but will deteriorate the combustion performance of the material.

[0141] Examples A1 to A6 are hydrophobic and flame-retardant EVOH resins prepared by the method of the present invention. Table 2 shows that the modified resin not only improved flame retardancy but also significantly increased its water contact angle. This indicates that the surface properties of the modified resin changed from polar to non-polar, thereby improving the interfacial bonding force when the resin is combined with non-polar materials, and also achieving an unexpected technical effect. The inventors of the present invention believe the reason for this technical effect is as follows: Although Comparative Example A2 contains phosphorus-containing groups, the hydroxyl groups are exposed and not grafted with long carbon chains (i.e., hydrophobic hydrocarbon groups), resulting in poor hydrophobicity; Comparative Example A3 does not graft phosphorus-containing groups, only long carbon chain hydrophobic groups, which improves hydrophobicity but significantly worsens flame retardancy. In contrast, the modified vinyl alcohol resin of the present invention contains both phosphorus-containing groups and hydrophobic groups containing four or more carbon hydrocarbon groups, thus possessing both hydrophobic and flame-retardant properties.

[0142] In this invention, the hydrophobic group containing four or more carbon hydrocarbon groups can be derived from a modified compound II containing four or more carbon hydrocarbon groups that can react with acyl chlorides or acids, such as one or more of n-hexylamine, cyclohexylamine, dodecyl alcohol, ethanolamine, and dodecyl chloride; or it can be derived from a phosphoric acid raw material containing hydrophobic groups, i.e., a modified compound I, such as dicyclohexylphosphochloride, phenylphosphodichloride, and diphenylphosphine chloride. As an example, by comparing Example A3 and Comparative Example A2, the test results show that when modified with phosphoric acid raw material (diphenylphosphine chloride), the phosphoric acid groups can promote the dehydration and char formation of the resin during combustion, thereby improving the flame retardant properties of the material. Since it contains hydrophobic groups, the hydrophobic properties are also improved. The flame retardant and hydrophobic properties of the product are improved simultaneously.

[0143] In summary, the hydrophobic and flame-retardant modified barrier resin of the present invention not only has higher flame retardancy than the original resin, but the non-polarity of the resin molecular chain also significantly improves its affinity with other non-polar resin components, thus improving the problems of poor interfacial interaction and poor flame retardancy faced by EVOH resin during use.

[0144] Preparation of gas-barrier flame-retardant resin compositions, single-layer films, or multi-layer composite films:

[0145] Example B1:

[0146] The modified ethylene-vinyl alcohol copolymer of Example A1 was selected. 100 parts of the modified ethylene-vinyl alcohol copolymer and 0.25 parts by weight of the composite antioxidant were placed in a low-speed mixer and stirred thoroughly. The mixture was then melt-blended through a twin-screw extruder at a temperature of 190℃~220℃ and a speed of 350r·pm. The extruded granules were dried in a 90℃ constant temperature oven for 3 hours to obtain the composition for sheet layer B.

[0147] According to the specified ratio, 50 parts by weight of polypropylene and 0.25 parts by weight of composite antioxidant are placed in a low-speed mixer and stirred thoroughly. Then, the mixture is melt-blended through a twin-screw extruder at a temperature of 190℃~220℃ and a speed of 350r.pm for extrusion granulation. The extruded granules are dried in a 90℃ constant temperature oven for 3 hours to obtain the composition for sheet layer A.

[0148] Using multi-layer co-extrusion, at 200–220°C, the above-mentioned raw materials were co-extruded into a three-layer composite film (i.e., a flame-retardant resin composition) using a three-layer composite film (composition for sheet layer A, composition for sheet layer B, and composition for sheet layer A arranged in a polypropylene / modified ethylene-vinyl alcohol copolymer / polypropylene configuration (i.e., ABA configuration), with a volume ratio of 25 / 100 / 25. Flame retardancy and barrier properties of the three-layer composite film were tested, and the results are shown in Table 4.

[0149] Example B2:

[0150] The three-layer composite membrane was prepared according to the method of Example B1, except that the modified ethylene-vinyl alcohol copolymer of Example A2 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0151] Example B3:

[0152] The three-layer composite membrane was prepared according to the method of Example B1, except that the modified ethylene-vinyl alcohol copolymer of Example A3 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0153] Example B4:

[0154] The modified ethylene-vinyl alcohol copolymer of Example A4 was selected. 50 parts by weight of polypropylene, 100 parts by weight of the modified ethylene-vinyl alcohol copolymer, and 0.25 parts by weight of the composite antioxidant were placed in a low-speed mixer and stirred thoroughly. The mixture was then melt-blended through a twin-screw extruder at a temperature of 190°C to 220°C and a speed of 350 rpm. The extruded granules were dried in a 90°C constant temperature oven for 3 hours to obtain a flame-retardant resin composition. The composition was then calendered at 200°C to 220°C to obtain a single-layer film, which was then subjected to flame retardancy and barrier tests.

[0155] Example B5:

[0156] The three-layer composite membrane was prepared according to the method of Example B1, except that the modified ethylene-vinyl alcohol copolymer of Example A4 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0157] Example B6:

[0158] The three-layer composite membrane was prepared according to the method of Example B1, except that the modified ethylene-vinyl alcohol copolymer of Example A5 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0159] Example B7:

[0160] The three-layer composite membrane was prepared according to the method of Example B1, except that the modified ethylene-vinyl alcohol copolymer of Example A6 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0161] Comparative Example B1:

[0162] A monolayer membrane was prepared according to the method of Example B4, except that the product of Comparative Example A1 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A4.

[0163] Comparative Example B2:

[0164] The three-layer composite membrane was prepared according to the method of Example B1, except that the product of Comparative Example A1 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0165] Comparative Example B3:

[0166] According to the ratio, 100 parts by weight of polypropylene and 0.25 parts by weight of composite antioxidant are put into a low-speed mixer and stirred evenly. Then, the mixture is melt-blended through a twin-screw extruder at a temperature of 190℃~220℃ and a speed of 350r.pm for extrusion granulation. The extruded granules are dried in a 90℃ constant temperature oven for 3 hours to obtain polypropylene raw material.

[0167] Using multi-layer co-extrusion, the above polypropylene raw materials are extruded into a three-layer composite film at 200-220°C in a polypropylene / polypropylene / polypropylene arrangement (i.e., AAA). The volume ratio of the three layers is 25 / 100 / 25, and then flame retardancy and barrier tests are performed.

[0168] Comparative Example B4:

[0169] The three-layer composite membrane was prepared according to the method of Example B1, except that the product of Comparative Example A2 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0170] Comparative Example B5:

[0171] The three-layer composite membrane was prepared according to the method of Example B1, except that the product of Comparative Example A3 was used instead of the modified ethylene-vinyl alcohol copolymer of Example A1.

[0172] Example B8:

[0173] The modified ethylene-vinyl alcohol copolymer of Example A4 was selected. 50 parts by weight of polyethylene, 100 parts by weight of the modified ethylene-vinyl alcohol copolymer, and 0.25 parts by weight of the composite antioxidant were mixed thoroughly in a low-speed mixer. The mixture was then melt-blended using a twin-screw extruder at a temperature of 190°C–220°C and a speed of 350 rpm. The extruded granules were dried in a 90°C constant-temperature oven for 3 hours to obtain a flame-retardant resin composition. The flame-retardant resin composition was calendered into a film at 200–220°C, and then subjected to flame retardancy and barrier tests.

[0174] Comparative Example B6:

[0175] According to the specified ratio, 100 parts by weight of polyethylene and 0.25 parts by weight of composite antioxidant are placed in a low-speed mixer and thoroughly mixed. Then, the mixture is melt-blended through a twin-screw extruder at a temperature of 190℃~220℃ and a speed of 350r.pm for extrusion granulation. The extruded granules are dried in a 90℃ constant temperature oven for 3 hours to obtain a polyethylene composition. The material is then calendered into a film at 200~220℃ and then subjected to flame retardancy and barrier tests.

[0176] Example B9:

[0177] The modified ethylene-vinyl alcohol copolymer of Example A4 was selected. 100 parts of the modified ethylene-vinyl alcohol copolymer and 0.25 parts by weight of the composite antioxidant were placed in a low-speed mixer and stirred thoroughly. The mixture was then melt-blended through a twin-screw extruder at a temperature of 190°C to 220°C and a speed of 350 rpm. The extruded granules were dried in a 90°C constant temperature oven for 3 hours to obtain the composition for sheet layer B.

[0178] According to the specified ratio, 100 parts by weight of polyethylene and 0.25 parts by weight of composite antioxidant are placed in a low-speed mixer and stirred thoroughly. Then, the mixture is melt-blended through a twin-screw extruder at a temperature of 190℃~220℃ and a speed of 350r·pm for extrusion granulation. The extruded granules are dried in a 90℃ constant temperature oven for 3 hours to obtain the composition for sheet layer A.

[0179] Using multi-layer co-extrusion, at 200-220°C, the above-mentioned composition raw materials are co-extruded into a three-layer composite film using a composition for sheet layer A, a composition for sheet layer B, and a composition for sheet layer A arranged in a polyethylene / modified ethylene-vinyl alcohol copolymer / polyethylene pattern (i.e., ABA). The volume ratio of the three layers is 25 / 100 / 25, and then flame retardancy and barrier tests are performed.

[0180] Comparative Example B7:

[0181] According to the specified ratio, 100 parts by weight of polyethylene and 0.25 parts by weight of composite antioxidant are placed in a low-speed mixer and stirred thoroughly. Then, the mixture is melt-blended through a twin-screw extruder at a temperature of 190℃~220℃ and a speed of 350r·pm for extrusion granulation. The extruded granules are dried in a 90℃ constant temperature oven for 3 hours to obtain the polyethylene composition.

[0182] Using multi-layer co-extrusion, the above-mentioned polyethylene composition was extruded into a three-layer composite film at 200–220°C in a polyethylene / polyethylene / polyethylene arrangement, with a volume ratio of 25 / 100 / 25 for the three layers. Flame retardancy and barrier properties were then tested.

[0183] Example B10:

[0184] Using the modified ethylene-vinyl alcohol copolymer from Example A4, 50 parts by weight of polyethylene terephthalate, 100 parts by weight of the modified ethylene-vinyl alcohol copolymer, and 0.25 parts by weight of the composite antioxidant were mixed thoroughly in a low-speed mixer. The mixture was then melt-blended using a twin-screw extruder at a temperature of 240°C–260°C and a speed of 350 rpm. The extruded granules were dried in a 90°C constant-temperature oven for 3 hours to obtain a flame-retardant resin composition. The flame-retardant resin composition was calendered into a film at 240°C–260°C, and then subjected to flame retardancy and barrier tests.

[0185] Comparative Example B8:

[0186] According to the specified ratio, 100 parts by weight of polyethylene terephthalate and 0.25 parts by weight of composite antioxidant were placed in a low-speed mixer and stirred thoroughly. The mixture was then melt-blended through a twin-screw extruder at a temperature of 240℃~260℃ and a speed of 350 rpm. The extruded granules were dried in a 90℃ constant temperature oven for 3 hours to obtain the polyethylene terephthalate composition. The material was then calendered into a film at 240~260℃ for flame retardancy and barrier tests.

[0187] Example B11:

[0188] The modified ethylene-vinyl alcohol copolymer of Example A4 was selected. 50 parts by weight of ethylene-vinyl acetate copolymer, 100 parts by weight of modified ethylene-vinyl alcohol copolymer, and 0.25 parts by weight of composite antioxidant were added to a low-speed mixer and thoroughly stirred. The mixture was then melt-blended using a twin-screw extruder at a temperature of 180°C–200°C and a speed of 350 rpm. The extruded granules were dried in a 90°C constant-temperature oven for 3 hours to obtain a flame-retardant resin composition. The flame-retardant resin composition was calendered into a film at 180°C–200°C for flame retardancy and barrier tests.

[0189] Comparative Example B9:

[0190] 100 parts by weight of ethylene-vinyl acetate copolymer and 0.25 parts by weight of composite antioxidant were placed in a low-speed mixer and stirred thoroughly. The mixture was then melt-blended through a twin-screw extruder at a temperature of 180℃~200℃ and a speed of 350 rpm. The extruded granules were dried in a 90℃ constant temperature oven for 3 hours to obtain the ethylene-vinyl acetate copolymer composition. The composition was then calendered into a film at 180℃~200℃ and subjected to flame retardancy and barrier tests.

[0191] The formulations of the membranes in Examples B1 to B11 and Comparative Examples B1 to B9 are shown in Table 3 (all amounts in Table 3 are parts by weight). The properties of the membranes prepared in the examples and comparative examples are shown in Table 4. When using multilayer co-extrusion, the membranes obtained in each example and comparative example have the same thickness.

[0192] In Table 4, the standard number for the limiting oxygen index test is GB / T 2406.1-2008; the standard number for the glow wire ignition temperature test is GB / T 5169.13-2013; and the standard number for the gas permeability test is GB / T 40260-2021.

[0193] Verification method for whether a multilayer composite membrane can be completely torn apart: Cut along the interlayer plane of the membrane with a blade, then tear the membrane from the middle and observe whether a relatively smooth separation surface can be obtained.

[0194] Table 3

[0195]

[0196] Table 4

[0197]

[0198] As can be seen from the test results in Table 4, the resins in the composition, such as polypropylene and polyethylene, are highly flammable, and the calendered film has poor gas barrier properties. The method of this invention can prepare a halogen-free flame-retardant resin composition with good gas barrier properties. Comparing the examples and comparative examples in Table 4, it can be seen that the resin composition prepared by this invention not only has improved flame retardancy but also higher gas barrier properties than pure resin. This indicates that the addition of the modified ethylene-vinyl alcohol copolymer simultaneously improves the gas barrier properties and flame retardancy of the material.

[0199] A comparison of Example B5 and Comparative Example B2 shows that the unmodified EVOH results in poor flame retardant properties and poor interlayer bonding between the material and polypropylene. A comparison of Example B5 with Comparative Examples B4 and B5 reveals that modification with simple phosphate groups improves the flame retardant ability, but due to its strong surface polarity, the sample co-extruded with polypropylene is easily torn apart. Conversely, the sample with simple long carbon linkages exhibits stronger interlayer bonding with polypropylene, but poorer flame retardant properties.

[0200] By comparing Examples B4 and B5, and Examples B8 and B9, it can be seen that modified EVOH has good flame retardant properties, whether it is introduced into the film through blending or multilayer co-extrusion.

[0201] In summary, the flame-retardant resin composition of the present invention not only retains the barrier properties of the original vinyl alcohol resin, but also has good flame-retardant effect. When it is prepared into a multilayer film, the interlayers of the multilayer film have good affinity and stronger interlayer bonding force, achieving unexpected technical effects.

[0202] Although the present invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those skilled in the art. Furthermore, it should be understood that the aspects described in the invention, the parts of different embodiments, and the various features listed can be combined or interchanged in whole or in part. In the various embodiments described above, those embodiments referencing another embodiment can be appropriately combined with other embodiments, as will be understood by those skilled in the art. Moreover, those skilled in the art will understand that the foregoing description is merely illustrative and not intended to limit the invention.

Claims

1. A flame-retardant resin composition comprising a base resin, a modified vinyl alcohol resin, and optional additives; The modified vinyl alcohol resin comprises a polymer backbone and modifying groups grafted onto the polymer backbone; the polymer backbone is derived from a polymer raw material comprising the following polymer and / or derivatives thereof: ethylene-vinyl alcohol copolymer; The modified group includes a phosphorus-containing group and a hydrophobic hydrocarbon group, wherein the hydrophobic hydrocarbon group contains 4 or more carbon atoms; the phosphorus-containing group is derived from modified compound one, wherein modified compound one is selected from at least one of inorganic phosphoric acid and its derivatives, and organic phosphoric acid and its derivatives.

2. The flame-retardant resin composition according to claim 1, characterized in that: In the modified vinyl alcohol resin: The modification rate of the phosphorus-containing groups on the polymer raw material is 0-85 mol%, and not 0, preferably 10-30 mol%, based on the content of all hydroxyl groups in the polymer raw material being 100 mol%; and / or, The phosphorus-containing group is connected to the polymer backbone via one or more ester bonds; and / or, The molar ratio of the hydrophobic hydrocarbon group to phosphorus is 1:(1-3), preferably 1:(1.3-1.9); and / or, The hydrophobic hydrocarbon group is selected from chain hydrocarbon groups and / or cyclic hydrocarbon groups containing 4 or more carbon atoms, preferably from chain hydrocarbon groups and / or cyclic hydrocarbon groups containing 4 to 18 carbon atoms.

3. The flame-retardant resin composition according to claim 1, characterized in that: The modified compound is selected from at least one of halogen-containing inorganic phosphoric acid derivatives and halogen-containing organic phosphoric acid derivatives. Preferably, the halogen is selected from one or more of fluorine, chlorine, bromine, and iodine. More preferably, the modified compound is selected from one or more of phosphorus oxychloride, pyrophosphoryl chloride, dicyclohexylphosphoryl chloride, bis(dimethylamino)phosphoric acid, phenylphosphoryl dichloride, diphenylphosphine chloride, diethylphosphite chloride, and O,O-dimethylphosphoryl chloride; and / or, The hydrophobic hydrocarbon group is connected to the phosphorus-containing group via an ester bond, amide bond, or secondary valence bond, and / or the hydrophobic hydrocarbon group originates from the hydrophobic hydrocarbon group itself contained in the phosphorus-containing group; preferably, When the modified compound one does not contain a hydrophobic hydrocarbon group, the hydrophobic hydrocarbon group is derived from the modified compound two, which can react with acyl chloride or acid; preferably, the modified compound two is selected from at least one of organic amines, organic alcohols, and acyl chlorides containing the hydrophobic hydrocarbon group, and more preferably, the modified compound two is selected from at least one of n-hexylamine, cyclohexylamine, dodecyl alcohol, and dodecyl chloride.

4. The flame-retardant resin composition according to claim 1, characterized in that: The number-average molecular weight of the ethylene-vinyl alcohol copolymer is between 10,000 and 200,000, and / or the melt index of the ethylene-vinyl alcohol copolymer measured at 190°C and 2.16 kg is between 0.5 and 25 g / 10 min, and / or The ethylene-vinyl alcohol copolymer is derived from structural units of ethylene monomers, which account for 15% to 50% of the total molar amount of all structural units.

5. The flame-retardant resin composition according to claim 1, characterized in that: The phosphorus content in the modified vinyl alcohol resin is 2–30 wt%, preferably 3–18 wt%, with the total mass of the modified vinyl alcohol resin being 100 wt%; and / or, Test sample one of the modified vinyl alcohol resin material was prepared according to the contents described in section "7 Specimen" of GB / T 30693-2014. The test sample one of the modified vinyl alcohol resin material was tested according to the test method described in section "10 Test Procedure" of GB / T 30693-2014. The water contact angle of the test sample one of the modified vinyl alcohol resin material was not less than 100°, preferably 110-140°; and / or, Test sample two of the modified vinyl alcohol resin material was prepared according to the contents described in section "7 Sample Preparation" of GB / T 2406.2-2009. The test sample two of the modified vinyl alcohol resin material was tested according to the test method described in section "8 Procedure for Determining Oxygen Index" of GB / T 2406.2-2009. The limiting oxygen index of the test sample two of the modified vinyl alcohol resin material was not less than 22%.

6. The flame-retardant resin composition according to claim 1, characterized in that: The modified vinyl alcohol resin is prepared by the following method, the preparation method comprising: In the presence of an acid-binding agent, the polymer raw material is grafted with the modified compound in a solvent, wherein the modified compound is selected from at least one of inorganic phosphoric acid and its derivatives, and organic phosphoric acid and its derivatives. When the modified compound one contains the hydrophobic hydrocarbon group, the modified vinyl alcohol resin is obtained after the grafting reaction one; or, When the modified compound one does not contain the hydrophobic hydrocarbon group, after the first grafting reaction, the modified compound two containing the hydrophobic hydrocarbon group is further subjected to a second grafting reaction to obtain the modified vinyl alcohol resin. The polymer raw material comprises ethylene-vinyl alcohol copolymer and / or its derivatives.

7. The flame-retardant resin composition according to any one of claims 1 to 6, characterized in that: The base resin is one or more thermoplastic resins; preferably, the base resin is selected from one or more of the following resins and their derivatives: polyolefins, polyoxymethylene, nylon, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, polycarbonate, polyphenylene ether, polyphenylene sulfide, epoxy resin, unsaturated polyester, vinyl resin; and / or, The additives are selected from one or more of the following: antioxidants, anti-aging agents, mold release agents, fillers, colorants, heat stabilizers, antibacterial agents, lubricants, plasticizers, and antistatic agents; and / or, The modified vinyl alcohol resin content is 50 to 400 parts by weight, preferably 150 to 250 parts, relative to 100 parts of the base resin.

8. A method for preparing a flame-retardant resin composition according to any one of claims 1 to 7, comprising mixing raw materials including the base resin, the modified vinyl alcohol resin and optional additives, and melt extruding.

9. A single-layer sheet, wherein the single-layer sheet is made of the flame-retardant resin composition according to any one of claims 1 to 7 or the flame-retardant resin composition obtained by the preparation method according to claim 8; Preferably, the single-layer sheet is a single-layer film.

10. A multilayer composite sheet, wherein the raw material of the multilayer composite sheet is the flame-retardant resin composition according to any one of claims 1 to 7; in, The base resin and the modified vinyl alcohol resin are respectively located in different sheet layers of the multilayer sheet, the multilayer sheet including sheet layer A formed containing the base resin and optional additives; the multilayer sheet also includes sheet layer B formed containing the modified vinyl alcohol resin and optional additives.

11. The multilayer composite sheet according to claim 10, characterized in that: The multilayer sheet is a multilayer film; and / or, The multilayer sheet is a three-layer sheet, with sheet layer B located in the middle of the three layers and having an ABA structure; preferably, Based on weight, the content of the modified vinyl alcohol resin is 50 to 400 parts, preferably 150 to 250 parts, relative to 100 parts of the base resin in the three-layer sheet; more preferably, the content of the base resin in the two sheet layers A is equal.

12. A method for preparing the multilayer composite sheet according to claim 10 or 11, comprising: Raw materials containing a base resin and optional additives are mixed and melt-extruded to obtain a composition for sheet layer A; Raw materials containing modified vinyl alcohol resin and optional additives are mixed and melt-extruded to obtain a composition for sheet layer B. The composition for sheet layer A and the composition for sheet layer B are co-extruded according to the structure of a multilayer sheet to obtain the multilayer sheet; optionally, the multilayer sheet is prepared into a film to obtain a multilayer film.

13. The application of a flame-retardant resin composition according to any one of claims 1 to 7, or a single-layer sheet according to claim 9, or a multi-layer composite sheet according to claim 10 or 11, preferably in the fields of encapsulation and lining, in food packaging, electronic component encapsulation, and container lining.

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