Crosslinkable polyethylene blend as well as preparation method and application thereof

Abstract

The invention discloses a crosslinkable polyethylene blend as well as a preparation method and application thereof. Wherein the crosslinkable polyethylene blend is prepared from the following components in parts by weight: 80 to 120 parts of polyethylene basic resin, 2 to 15 parts of a polar material, 0.1 to 5 parts of a peroxide crosslinking agent, 0.1 to 1 part of an antioxidant and 0.5 to 2 parts of a deodorant; the deodorant comprises a mixture of manganese-based organic acid salt, zinc-based organic acid salt and rare-earth-based organic acid salt. The deodorant is added into the crosslinkable polyethylene blend, so that the problem that a peroxide crosslinking agent can be decomposed to generate pungent smell in the heating process is solved, and the PEX lining layer meets the sanitation and safety requirements of the inner container of the water heater. And meanwhile, by adding the polar material into the crosslinkable polyethylene blend, the cohesiveness between the polyethylene matrix resin and the metal outer lining is improved, and the delaminating phenomenon is avoided in the use process, so that the requirement on the service life of the water heater inner container is met.

Description

Technical Field

[0001] The invention belongs to the technical field of water heater materials, and in particular relates to a cross-linkable polyethylene blend and a preparation method and application thereof. Background Art

[0002] Most of the current electric water heaters and solar water heaters use enamel inner tanks. Since the steel plate of the enamel inner tank is prone to hydrogen evolution and fish scale explosion, it leads to poor surface adhesion, and problems such as shrinkage holes or sand holes will appear at the welds. In addition, the material of the enamel inner tank itself is relatively brittle and easily damaged during transportation, so it is necessary to use a magnesium rod to protect the inner tank. However, magnesium rods are prone to produce magnesium slag during use, which will accelerate the formation of scale and pollute the water quality. Long-term use will also cause irritation to the user's skin. In order to solve the above problems, the prior art uses cross-linked polyethylene (PEX) rotational molding to prepare a steel-plastic composite inner tank, which has both the pressure-bearing capacity of steel and the anti-corrosion performance of PEX lining, does not require magnesium rod protection, and has better water quality. However, the PEX raw materials currently used for steel lining rotational molding have the following problems: 1) The raw materials have poor polarity. Even if the steel surface is subjected to complex surface treatments such as phosphating, the bonding strength between the steel plastic and the PEX lining is still low and easy to delaminate; 2) Most traditional rotational molding PEX raw materials use peroxide cross-linking agents (such as diisopropyl peroxide DCP). The peroxide cross-linking agent will decompose after the cross-linking reaction to produce a pungent odor. The pungent odor is not only unpleasant but also harmful to the human body. This problem is currently a pain point in this field. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present invention is to provide a cross-linkable polyethylene blend and a preparation method and application thereof. The present invention solves the problem that the peroxide cross-linking agent decomposes and produces a pungent odor during heating by adding a deodorant to the cross-linkable polyethylene blend, so that the PEX lining layer meets the hygienic and safety requirements of the water heater tank. At the same time, the present invention improves the adhesion between the polyethylene matrix resin and the metal outer lining by adding a polar material to the cross-linkable polyethylene blend, and no delamination occurs during use, thereby meeting the service life requirements of the water heater tank.

[0004] In one aspect of the present invention, the present invention provides a cross-linkable polyethylene blend. According to an embodiment of the present invention, the cross-linkable polyethylene blend comprises:

[0005] 80-120 parts by weight of a polyethylene base resin, 2-15 parts by weight of a polar material, 0.1-5 parts by weight of a peroxide crosslinking agent, 0.1-1 parts by weight of an antioxidant, and 0.5-2 parts by weight of a deodorant;

[0006] The deodorant comprises a mixture of manganese-based organic acid salts, zinc-based organic acid salts and rare earth-based organic acid salts.

[0007] According to the cross-linkable polyethylene blend of the embodiment of the present invention, the problem of the peroxide cross-linking agent decomposing and producing pungent odor during heating is solved by adding a deodorant to the cross-linkable polyethylene blend, so that the PEX lining layer meets the hygienic safety requirements of the water heater tank. At the same time, the present invention improves the adhesion between the polyethylene matrix resin and the metal outer lining by adding a polar material to the cross-linkable polyethylene blend, so that the metal outer lining only needs to undergo a simple degreasing step, without the need for complicated sandblasting, pickling, phosphating, etc. to achieve the required bonding strength for use, and the peel strength between the metal outer lining and the PEX inner lining layer reaches 285N / cm-380N / cm, and no delamination will occur during use, thereby meeting the service life requirements of the water heater tank.

[0008] In addition, the cross-linkable polyethylene blend according to the above embodiment of the present invention may also have the following additional technical features:

[0009] In some embodiments of the present invention, the mass ratio of the manganese-based organic acid salt, the zinc-based organic acid salt and the rare earth-based organic acid salt is (55-65):(25-35):(8-12).

[0010] In some embodiments of the present invention, the peroxide crosslinking agent includes at least one of di-tert-butyl diisopropylbenzene peroxide, diisopropylbenzene peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and di-tert-butyl peroxide.

[0011] In some embodiments of the present invention, the manganese-based organic acid salt includes at least one of manganese lactate, manganese octadecanoate and manganese neodecanoate.

[0012] In some embodiments of the present invention, the zinc-based organic acid salt includes at least one of zinc lactate, zinc citrate and zinc ricinoleate.

[0013] In some embodiments of the present invention, the rare earth-based organic acid salt includes at least one of rare earth stearate, rare earth salicylate and rare earth citrate.

[0014] In some embodiments of the present invention, the polar material includes at least one of isocyanate, acrylate, unsaturated carboxylic acid, polyolefin grafted with anhydride or ester derivative, epoxy resin and unsaturated polyester resin.

[0015] In some embodiments of the present invention, the antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxy-phenyl)propionate and 4,4'-thiobis(6-tert-butyl-3-methyl)phenol.

[0016] In another aspect of the present invention, the present invention provides a water heater tank. According to an embodiment of the present invention, the water heater tank includes a metal outer lining and a PEX inner lining layer arranged close to the inner side of the metal outer lining, and the PEX inner lining layer is formed by heating and cross-linking the cross-linkable polyethylene blend of the above embodiment. As a result, the PEX inner lining layer of the water heater tank has a small odor and can meet the safety and sanitation requirements for bathing water. At the same time, the adhesion between the metal outer lining and the PEX inner lining layer of the water heater tank is strong, and there will be no delamination during use, thereby meeting the service life requirements of the water heater tank.

[0017] In addition, the cross-linkable polyethylene blend according to the above embodiment of the present invention may also have the following additional technical features:

[0018] In some embodiments of the present invention, the peel strength between the metal outer lining and the PEX inner lining layer is 285N / cm-380N / cm.

[0019] In some embodiments of the present invention, the cross-linking degree of the PEX lining layer is 72%-76%.

[0020] In a third aspect of the present invention, the present invention provides a method for preparing the above-mentioned water heater inner tank. According to an embodiment of the present invention, the method comprises:

[0021] (1) Pre-treat the metal lining;

[0022] (2) The cross-linkable polyethylene blend is loaded into the inner side of the metal outer liner, placed in a rotational molding machine, and rotationally molded to form a PEX inner lining layer on the inner side of the metal outer liner.

[0023] According to the method for preparing the water heater inner tank in the embodiment of the present invention, the water heater inner tank prepared by the method has relatively excellent high temperature resistance, boiling resistance and moisture heat resistance, and can effectively prevent the substrate from high temperature oxidation and corrosion; at the same time, it also has excellent anti-fingerprint performance, no fingerprints are left when touched by fingers, and oil stains are easy to clean. The preparation method is simple in steps and easy to operate.

[0024] In addition, the method for preparing a water heater tank according to the above embodiment of the present invention may also have the following additional technical features:

[0025] In some embodiments of the present invention, the rotational molding temperature is 220° C.-280° C., and the rotational molding time is 15 min-35 min.

[0026] In the fourth aspect of the present invention, the present invention proposes a water heater. According to an embodiment of the present invention, the water heater has the water heater inner tank of the above embodiment or the water heater inner tank prepared by the method described in the above embodiment. Therefore, the water heater has all the advantages of the water heater inner tank of the above embodiment. Specifically, the PEX lining layer of the water heater inner tank of the water heater has a small odor and can meet the safety and sanitation requirements for bathing water; at the same time, the metal outer lining of the water heater inner tank and the PEX lining layer have strong adhesion, and there will be no delamination during use, thereby meeting the service life requirements of the water heater inner tank, thereby further meeting the needs of consumers.

[0027] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0029] Figure 1 The present invention is a schematic flow chart of a method for preparing a water heater tank according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0031] In one aspect of the present invention, the present invention proposes a cross-linkable polyethylene blend. According to an embodiment of the present invention, the cross-linkable polyethylene blend is used to prepare a water heater liner, and the cross-linkable polyethylene blend includes: 80-120 parts by weight of a polyethylene base resin, 2-15 parts by weight of a polar material, 0.1-5 parts by weight of a peroxide cross-linking agent, 0.1-1 parts by weight of an antioxidant, and 0.5-2 parts by weight of a deodorant; the deodorant includes a mixture of a manganese-based organic acid salt, a zinc-based organic acid salt, and a rare earth-based organic acid salt. Therefore, the present invention solves the problem that the peroxide cross-linking agent will decompose and produce a pungent odor during heating by adding a deodorant to the cross-linkable polyethylene blend, so that the PEX lining layer meets the hygienic and safety requirements of the water heater liner. At the same time, the present invention improves the adhesion between the polyethylene matrix resin and the metal outer lining by adding polar materials to the cross-linkable polyethylene blend, so that the metal outer lining only needs to undergo a simple degreasing step, and does not require complicated sandblasting, pickling, phosphating, etc. to achieve the bonding strength required for use. The peel strength between the metal outer lining and the PEX inner lining layer reaches 285N / cm-380N / cm, and no delamination will occur during use, thereby meeting the service life requirements of the water heater tank.

[0032] The principle by which the water heater tank proposed by the present invention can achieve the above beneficial effects is described in detail below:

[0033] In the prior art, cross-linked polyethylene (PEX) is used for rotational molding to prepare a steel-plastic composite liner, which has both the pressure-bearing capacity of steel and the anti-corrosion performance of a PEX liner. In the process of forming the PEX liner, since the heat resistance of the polyethylene base resin does not meet the use standard of the water heater, it is necessary to use a peroxide cross-linking agent to cause the polyethylene base resin to undergo a cross-linking reaction under certain conditions to form a cross-linked polyethylene liner. However, the peroxide cross-linking agent will decompose and produce a pungent odor after the cross-linking reaction. The pungent odor is not only unpleasant but also harmful to the human body. For example, DCP is easily decomposed into gases such as acetophenone, methane, and 2-phenylisopropanol, especially acetophenone, which can cause severe irritation to the human eyes or respiratory tract, and BIBP is easily decomposed into steam such as tert-butyl alcohol and acetone. This problem is currently a pain point in this field. People in this field have tried many methods, but none of them can effectively solve the problem of pungent odor.

[0034] In order to solve the above technical problems, the present invention adds a deodorant to the crosslinkable polyethylene blend, and the deodorant includes a mixture of manganese-based organic acid salts, zinc-based organic acid salts and rare earth-based organic acid salts, which can undergo irreversible coordination and complexation reaction with alcohol molecules, ammonia molecules, sulfhydryl molecules, ketone compounds and the like of odor sources to form coordination bonds, generate non-volatile, non-toxic and tasteless high-boiling macromolecular coordination complexes, and can completely remove various odor molecules, especially having a unique effect on the odor generated by the decomposition of peroxide crosslinking agents. For example, the deodorant can undergo irreversible coordination and complexation reaction with gases such as acetophenone, methane, and 2-phenylisopropanol generated by the decomposition of DCP after the crosslinking reaction, or with steam such as tert-butyl alcohol and acetone generated by the decomposition of BIBP to form coordination bonds, generate non-volatile, non-toxic and tasteless high-boiling macromolecular coordination complexes, thereby removing various odor molecules generated by the decomposition of peroxide crosslinking agents. In addition, the metal salt deodorant can also catalyze the decomposition of some odor molecules. Therefore, the present invention solves the problem that the peroxide cross-linking agent decomposes and produces pungent odor during heating by adding a deodorant to the cross-linkable polyethylene blend, so that the PEX lining layer meets the hygienic and safety requirements of the water heater tank.

[0035] It should be noted that the manganese-based organic acid salt, the zinc-based organic acid salt and the rare earth-based organic acid salt have a synergistic effect on each other. The above-mentioned technical effect can only be achieved by the cooperation of the three. The technical effect of the present invention cannot be achieved without any one of them.

[0036] In addition, in the prior art, the polarity of the cross-linked PEX lining layer is poor. Even if the steel surface is subjected to complex surface treatments such as phosphating, the bonding strength between the steel plastic and the PEX lining is still low and easy to delaminate. In order to solve this technical problem, the present invention adds polar materials to the cross-linkable polyethylene blend. Polar groups exist in the polar materials. The polar groups in the polar materials can react with the hydroxyl groups on the metal outer lining to generate chemical bonds, thereby improving the bonding between the PEX lining and the metal outer lining, so that the metal outer lining only needs to undergo a simple degreasing step, without the need for complex sandblasting, pickling, phosphating, etc. to achieve the bonding strength required for use, so that the peel strength between the metal outer lining and the PEX lining layer reaches 285N / cm-380N / cm, and no delamination will occur during use, thereby meeting the service life requirements of the water heater tank.

[0037] In the embodiment of the present invention, when the cross-linkable polyethylene blend undergoes a cross-linking reaction on the inner side of the metal outer lining, under the action of the peroxide cross-linking agent, the polyethylene base resin itself undergoes a cross-linking reaction to form a cross-linked polyethylene lining. When the polar material is selected from a polymer material (such as isocyanate, acrylate, unsaturated carboxylic acid, polyolefin grafted with anhydride or ester derivatives, epoxy resin and unsaturated polyester resin, etc.), a cross-linking reaction also occurs between the polyethylene base resin and the polar material. The role of the antioxidant is to prevent oxidation and aging of the PEX lining.

[0038] According to some specific embodiments of the present invention, the mass ratio of manganese-based organic acid salt, zinc-based organic acid salt and rare earth-based organic acid salt can be (55-65): (25-35): (8-12). By limiting the mass ratio of manganese-based organic acid salt, zinc-based organic acid salt and rare earth-based organic acid salt to the range of (55-65): (25-35): (8-12), the effect of removing various odor molecules generated by the decomposition of the peroxide cross-linking agent is further ensured. Preferably, the mass ratio of manganese-based organic acid salt, zinc-based organic acid salt and rare earth-based organic acid salt is 60:30:10.

[0039] In the embodiments of the present invention, the specific type of peroxide crosslinking agent is not particularly limited, as long as it can promote the crosslinking reaction of the polyethylene base resin at a specific temperature. As some specific examples, the peroxide crosslinking agent includes at least one of di-tert-butyl peroxide diisopropylbenzene (BIBP), diisopropylbenzene peroxide (DCP), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and di-tert-butyl peroxide. The above types of peroxide crosslinking agents can make the crosslinking degree of the PEX liner layer higher than 70%, so that it can meet the requirement of being able to be used for a long time at 80 degrees Celsius. Di-tert-butyl diisopropylbenzene peroxide (BIBP) is preferred because it decomposes to produce a small amount of tert-butyl alcohol and acetone vapor during heating, and undergoes irreversible coordination and complexation reaction with deodorant (i.e., a mixture of manganese-based organic acid salts, zinc-based organic acid salts and rare earth-based organic acid salts) to form a coordination bond, generating a non-volatile, non-toxic and tasteless high-boiling macromolecular coordination complex, which can completely remove the vapor generated by the decomposition of BIBP. In the present invention, BIBP is combined with a deodorant, and its deodorization effect is better. However, the DCP cross-linking agent decomposes to produce a large amount of acetophenone, methane, 2-phenylisopropyl alcohol, etc. during heating, and acetophenone in particular can cause severe irritation to human eyes or respiratory tract.

[0040] In the embodiment of the present invention, the specific type of the above-mentioned manganese-based organic acid salt is not particularly limited. As some specific examples, the manganese-based organic acid salt includes at least one of manganese lactate, manganese octadecanoate and manganese neodecanoate.

[0041] In the embodiment of the present invention, the specific type of the zinc-based organic acid salt is not particularly limited. As some specific examples, the zinc-based organic acid salt includes at least one of zinc lactate, zinc citrate and zinc ricinoleate.

[0042] In the embodiments of the present invention, the specific types of the rare earth-based organic acid salts are not particularly limited. As some specific examples, the rare earth-based organic acid salts include at least one of rare earth stearate, rare earth salicylate and rare earth citrate. Among them, the rare earth stearate includes at least one of cerium stearate and lanthanum stearate, the rare earth salicylate includes at least one of cerium salicylate and lanthanum salicylate, and the rare earth citrate includes at least one of cerium citrate and lanthanum citrate.

[0043] In the embodiments of the present invention, the specific types of the above polar materials are not particularly limited. As some specific examples, the polar materials include but are not limited to at least one of polyolefins, epoxy resins and unsaturated polyester resins grafted with isocyanates, acrylates, unsaturated carboxylic acids, anhydrides or ester derivatives. Among them, epoxy resins and unsaturated polyester resins both contain polar groups, which can react with hydroxyl groups on the metal outer lining to form chemical bonds, thereby improving the adhesion between the PEX lining and the metal outer lining. The polar materials formed by grafting isocyanates, acrylates, unsaturated carboxylic acids, anhydrides or ester derivatives on polyolefins also contain polar groups, which can also react with hydroxyl groups on the metal outer lining to form chemical bonds, thereby improving the adhesion between the PEX lining and the metal outer lining. The grafting rate on polyolefins is also not particularly limited, and is generally selected between 1% and 10%.

[0044] In an embodiment of the present invention, the specific type of the above-mentioned antioxidant is not particularly limited. As some specific examples, the antioxidant includes but is not limited to at least one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxy-phenyl)propionate]pentaerythritol ester and 4,4'-thiobis(6-tert-butyl-3-methyl)phenol.

[0045] In another aspect of the present invention, the present invention provides a water heater tank. According to an embodiment of the present invention, the water heater tank includes a metal outer lining and a PEX inner lining layer arranged close to the inner side of the metal outer lining, and the PEX inner lining layer is formed by heating and cross-linking the cross-linkable polyethylene blend of the above embodiment. As a result, the PEX inner lining layer of the water heater tank has a small odor and can meet the safety and sanitation requirements for bathing water. At the same time, the adhesion between the metal outer lining and the PEX inner lining layer of the water heater tank is strong, and there will be no delamination during use, thereby meeting the service life requirements of the water heater tank.

[0046] Specifically, the metal outer lining can achieve the required bonding strength by undergoing only a simple degreasing step without complicated steps such as sandblasting, pickling, and phosphating, so that the peel strength between the metal outer lining and the PEX inner lining layer can reach 285N / cm-380N / cm.

[0047] In the embodiment of the present invention, the specific type of the metal outer lining is not particularly limited, and may be, for example, a carbon steel outer lining.

[0048] According to some specific embodiments of the present invention, the cross-linking degree of the PEX lining layer can be 72%-76%, so that the PEX lining layer can meet the requirement of being able to be used at 80 degrees Celsius for a long time.

[0049] As some specific examples, the thickness of the PEX inner lining layer is 2-4 mm, and the thickness of the metal outer lining is not particularly limited.

[0050] In the third aspect of the present invention, the present invention provides a method for preparing the above-mentioned water heater inner tank. Figure 1 , the method comprising:

[0051] S100: Pre-treat the metal lining.

[0052] In this step, the metal outer lining is pretreated to remove the oil and rust on the surface of the metal outer lining so that the PEX inner lining layer can be better bonded to the metal outer lining.

[0053] S200: The cross-linkable polyethylene blend is loaded into the inner side of the metal outer liner, placed in a rotational molding machine, and rotationally molded to form a PEX inner lining layer inside the metal outer liner.

[0054] According to some specific embodiments of the present invention, the rotational molding temperature can be 220°C-280°C (for example, it can be 220 / 230 / 240 / 250 / 260 / 270 / 280°C, etc.), and the rotational molding time can be 15min-35min (for example, it can be 15 / 20 / 25 / 30 / 35min).

[0055] Before the cross-linkable polyethylene blend is loaded into the inner side of the metal outer liner, the polyethylene base resin, polar material, peroxide cross-linking agent, antioxidant and deodorant are first melt-blended at 130-150° C. (for example, melt-blended in a twin-screw extruder), and then granulated to obtain the cross-linkable polyethylene blend.

[0056] According to the method for preparing the water heater inner tank in the embodiment of the present invention, the PEX inner lining layer of the water heater inner tank prepared has less odor and can meet the safety and sanitation requirements for bathing water. At the same time, the metal outer lining of the water heater inner tank and the PEX inner lining layer have strong adhesion, and no delamination will occur during use, thereby meeting the service life requirements of the water heater inner tank. The preparation method is simple and easy to implement.

[0057] In the fourth aspect of the present invention, the present invention proposes a water heater. According to an embodiment of the present invention, the water heater has the water heater inner tank of the above embodiment or the water heater inner tank prepared by the method described in the above embodiment. Therefore, the water heater has all the advantages of the water heater inner tank of the above embodiment. Specifically, the PEX lining layer of the water heater inner tank of the water heater has a small odor and can meet the safety and sanitation requirements for bathing water; at the same time, the metal outer lining of the water heater inner tank and the PEX lining layer have strong adhesion, and there will be no delamination during use, thereby meeting the service life requirements of the water heater inner tank, thereby further meeting the needs of consumers.

[0058] Specifically, the water heater may be an electric water heater, a solar water heater or the like.

[0059] The embodiments of the present invention are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention. In addition, if not explicitly stated, all reagents used in the following embodiments are commercially available, or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0060] Example 1

[0061] This embodiment provides a water heater inner tank, and the preparation method thereof includes:

[0062] 1) 100 g of linear low-density polyethylene LLDPE1802, 1 g of peroxide crosslinking agent BIBP, 5 g of unsaturated polyester resin HS8706, 0.1 g of antioxidant Irganox 1010 and 0.5 g of deodorant are extruded, granulated and ground at 140° C. and 75 rpm through a twin-screw extruder to obtain a crosslinkable polyethylene blend; the deodorant is a mixture of manganese lactate, zinc ricinoleate and cerium citrate, and the mass ratio of manganese lactate, zinc ricinoleate and cerium citrate is 60:30:10.

[0063] 2) Degrease and rust the carbon steel welded liner.

[0064] 3) The cross-linkable polyethylene blend is loaded into the inner side of the carbon steel outer liner, placed in a rotational molding machine, and rotationally molded. The rotational molding temperature is 230° C., the heating time is 25 min, and the cooling time is 15 min, so as to form a PEX lining layer inside the carbon steel outer liner.

[0065] Example 2

[0066] The difference between this embodiment and embodiment 1 is only that:

[0067] 1) 100 g of linear low-density polyethylene LLDPE1802, 1 g of peroxide crosslinking agent BIBP, 8 g of epoxy resin E12, 0.1 g of antioxidant Irganox 1010 and 1 g of deodorant are extruded, granulated and ground at 140° C. and 75 rpm through a twin-screw extruder to obtain a crosslinkable polyethylene blend; the deodorant is a mixture of manganese lactate, zinc ricinoleate and cerium citrate, and the mass ratio of manganese lactate, zinc ricinoleate and cerium citrate is 60:30:10.

[0068] The other steps are the same as those in Example 1.

[0069] Example 3

[0070] The difference between this embodiment and embodiment 1 is only that:

[0071] 1) 100 g of linear low-density polyethylene LLDPE1802, 1 g of peroxide crosslinking agent BIBP, 10 g of epoxy resin E12, 0.1 g of antioxidant Irganox 1010 and 1.5 g of deodorant are extruded, granulated and ground at 140° C. and 75 rpm through a twin-screw extruder to obtain a crosslinkable polyethylene blend; the deodorant is a mixture of manganese lactate, zinc ricinoleate and cerium citrate, and the mass ratio of manganese lactate, zinc ricinoleate and cerium citrate is 60:30:10.

[0072] The other steps are the same as those in Example 1.

[0073] Example 4

[0074] 1) 100 g of linear low-density polyethylene LLDPE1802, 1 g of peroxide crosslinking agent BIBP, 8 g of maleic anhydride grafted polyolefin MA-LLDPE (grafting rate is 1.2 wt%), 0.1 g of antioxidant Irganox 1010 and 2 g of deodorant are extruded, granulated and ground at 140° C. and 75 rpm through a twin-screw extruder to obtain a crosslinkable polyethylene blend; the deodorant is a mixture of manganese lactate, zinc ricinoleate and cerium citrate, and the mass ratio of manganese lactate, zinc ricinoleate and cerium citrate is 60:30:10.

[0075] The other steps are the same as those in Example 1.

[0076] Example 5

[0077] 1) 80g of linear low-density polyethylene LLDPE1802, 2g of peroxide crosslinking agent BIBP, 10g of epoxy resin E12, 0.5g of antioxidant Irganox 1010 and 1.5g of deodorant are extruded, granulated and ground at 140°C and 75rpm through a twin-screw extruder to obtain a crosslinkable polyethylene blend; the deodorant is a mixture of manganese octadecanoate, zinc lactate and cerium salicylate, and the mass ratio of manganese octadecanoate, zinc lactate and cerium salicylate is 55:35:8.

[0078] The other steps are the same as those in Example 3.

[0079] Example 6

[0080] 1) 120 g of linear low-density polyethylene LLDPE1802, 4 g of peroxide crosslinking agent BIBP, 10 g of epoxy resin E12, 1 g of antioxidant Irganox 1010 and 1.5 g of deodorant are extruded, granulated and ground at 140° C. and 75 rpm through a twin-screw extruder to obtain a crosslinkable polyethylene blend; the deodorant is a mixture of manganese neodecanoate, zinc citrate and cerium stearate, and the mass ratio of manganese neodecanoate, zinc citrate and cerium stearate is 65:25:12.

[0081] The other steps are the same as those in Example 3.

[0082] Example 7

[0083] 1) 100 g of linear low-density polyethylene LLDPE1802, 1 g of peroxide crosslinking agent DCP, 10 g of epoxy resin E12, 0.1 g of antioxidant Irganox 1010 and 1.5 g of deodorant are extruded, granulated and ground at 140° C. and 75 rpm through a twin-screw extruder to obtain a crosslinkable polyethylene blend; the deodorant is a mixture of manganese lactate, zinc ricinoleate and cerium citrate, and the mass ratio of manganese lactate, zinc ricinoleate and cerium citrate is 60:30:10.

[0084] The other steps are the same as those in Example 4.

[0085] Comparative Example 1

[0086] No deodorant was added in this comparative example, and other contents were the same as those in Example 3.

[0087] Comparative Example 2

[0088] In this comparative example, epoxy resin E12 is not added, and other contents are the same as those in Example 3.

[0089] Comparative Example 3

[0090] No deodorant was added in this comparative example, and other contents were the same as those in Example 7.

[0091] The data of each component of Examples 1-7 and Comparative Examples 1-3 are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] The crosslinking degree of the PEX liner of Examples 1-7 and Comparative Examples 1-3 was determined according to ASTM D 2765. The test method is as follows: a PEX sample block with a mass of W1 (about 0.3 g) was cut from the inner liner, chopped and placed in a 100 mL stainless steel mesh (the specifications of the mesh refer to the requirements of ASTM D 2765); the sample was extracted in a xylene solution at 170°C for 24 hours, then taken out, and then dried in a vacuum drying oven at 90°C for 6 hours, and the mass was weighed as W2.

[0096] Calculate the degree of crosslinking: degree of crosslinking % = (W2 / W1) x 100%.

[0097] The peel strength (N / cm) of the PEX liner of Examples 1-7 and Comparative Examples 1-3 was measured according to GB / T23257-2017. The test method is as follows: a strip with a width of 1 cm and a length greater than 20 cm is scratched on the PEX liner of the liner product, and the scratch depth reaches the metal part. One end of the strip is peeled off from the metal part by at least 2 cm, and the strip is pulled up at a speed of 10 mm / min using a tensile testing machine; the stress value of the tensile testing machine is read, and after the tension is stable, the average value after stabilization is taken as the peel strength.

[0098] The odor detection method is as follows: 5 odor testers test the odor of the liner just produced N0, the odor after being placed in the air for 24 hours Ng 24 、Odor after being placed in the air for 48 hours Ng 48 , the smell after water treatment N w , divided into 6 levels: 1 = no odor, 2 = slight odor, 3 = odor, but not irritating, 4 = irritating odor, 5 = strong irritating odor, 6 unbearable odor. Then calculate the average of the odor levels detected by the five odor testers, odor level N = (N1 + N2 + N3 + N4 + N5) / 5, the test results are shown in Table 2.

[0099] Table 2

[0100]

[0101]

[0102] As can be seen from Table 1, the crosslinking degree of the PEX liner of Examples 1-7 is above 72.1%, the peel strength is above 287.5 N / cm, the odor N0 of the liner just produced is below 3.2 level, and the odor Ng after being placed in the air for 24 hours is 24 All are below 2.5 level, and the odor after being placed in the air for 48 hours is Ng 48 All are below 2.2 level, and the odor after water treatment is N w All are below level 1.5, meeting the hygiene and safety requirements for the water heater tank.

[0103] Compared with Comparative Example 1, the odor of the inner container prepared in Example 3 is significantly reduced in various states, and it can be seen that the deodorizing effect after adding the deodorant is very obvious.

[0104] Compared with Example 7, the odor of the inner liner prepared in Example 3 is significantly lower in various states. It can be seen that by using BIBP as a peroxide cross-linking agent, the odor of the inner liner in various states is significantly reduced.

[0105] Compared with Comparative Example 2, the peel strength of the PEX liner prepared in Example 3 is significantly improved. It can be seen that the addition of polar materials significantly improves the peel strength of the PEX liner, meeting the service life requirements of the water heater tank.

[0106] Compared with Comparative Example 3, the odor of the inner container prepared in Example 7 is significantly reduced in various states, and it can be seen that the deodorizing effect after adding the deodorant is very obvious.

[0107] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0108] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A cross-linkable polyethylene blend, characterized in that: include: 80-120 parts by weight of a polyethylene base resin, 2-15 parts by weight of a polar material, 0.1-5 parts by weight of a peroxide crosslinking agent, 0.1-1 parts by weight of an antioxidant, and 0.5-2 parts by weight of a deodorant; The deodorant comprises a mixture of manganese-based organic acid salts, zinc-based organic acid salts and rare earth-based organic acid salts.

2. The cross-linkable polyethylene blend according to claim 1, characterized in that The mass ratio of the manganese-based organic acid salt, the zinc-based organic acid salt and the rare earth-based organic acid salt is (55-65):(25-35):(8-12).

3. The cross-linkable polyethylene blend according to claim 1, characterized in that: The peroxide crosslinking agent includes at least one of di-tert-butyl diisopropylbenzene peroxide, diisopropylbenzene peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and di-tert-butyl peroxide.

4. The cross-linkable polyethylene blend according to claim 1, characterized in that: The manganese-based organic acid salt includes at least one of manganese lactate, manganese octadecanoate and manganese neodecanoate.

5. The cross-linkable polyethylene blend according to claim 1, characterized in that: The zinc-based organic acid salt includes at least one of zinc lactate, zinc citrate and zinc ricinoleate.

6. The cross-linkable polyethylene blend according to claim 1, characterized in that: The rare earth-based organic acid salt includes at least one of rare earth stearate, rare earth salicylate and rare earth citrate.

7. The cross-linkable polyethylene blend according to any one of claims 1 to 6, characterized in that: The polar material includes at least one of isocyanate, acrylate, unsaturated carboxylic acid, polyolefin grafted with anhydride or ester derivative, epoxy resin and unsaturated polyester resin.

8. The cross-linkable polyethylene blend according to any one of claims 1 to 6, characterized in that: The antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxy-phenyl) propionate and 4,4'-thiobis(6-tert-butyl-3-methyl)phenol.

9. A water heater tank, characterized in that: It comprises a metal outer liner and a PEX inner liner layer arranged close to the inner side of the metal outer liner, wherein the PEX inner liner layer is formed by heating and cross-linking the cross-linkable polyethylene blend described in any one of claims 1 to 8.

10. The water heater inner tank according to claim 9, characterized in that: The peel strength between the metal outer lining and the PEX inner lining layer is 285N / cm-380N / cm.

11. The water heater inner tank according to claim 9, characterized in that: The cross-linking degree of the PEX lining layer is 72%-76%.

12. A method for preparing a water heater tank according to any one of claims 9 to 11, characterized in that: include: (1) Pre-treat the metal lining; (2) The cross-linkable polyethylene blend is loaded into the inner side of the metal outer liner, placed in a rotational molding machine, and rotationally molded to form a PEX inner lining layer on the inner side of the metal outer liner.

13. The method according to claim 12, characterized in that The temperature of the rotational molding is 220° C.-280° C., and the time of the rotational molding is 15 min-35 min.

14. A water heater, characterized in that: A water heater inner tank according to any one of claims 9 to 11 or a water heater inner tank prepared by the method according to claim 12 or 13.

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