Water heater inner container and preparation method and application thereof

Abstract

The invention discloses a water heater inner container and a preparation method and application thereof. The inner container of the water heater comprises a metal pressure bearing layer; the polyethylene bonding layer is arranged on the inner side of the metal pressure-bearing layer, the polyethylene bonding layer is formed by adopting a polyethylene blend, and the polyethylene blend comprises 80-120 parts by weight of polyethylene basic resin, 2-15 parts by weight of a polar material and 0.1-1 part by weight of an antioxidant; and the heat-resistant organic polymer anti-corrosion layer is arranged on one side, far away from the metal pressure-bearing layer, of the polyethylene bonding layer. The polyethylene bonding layer and the heat-resistant organic polymer anti-corrosion layer of the water heater inner container are free of pungent smell, and the safety and sanitation requirements of bath water can be met. Meanwhile, the cohesiveness between the metal pressure-bearing layer and the polyethylene bonding layer of the water heater inner container is high, the delaminating phenomenon cannot occur in the using process, and therefore the requirement for 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 water heater inner tank and a preparation method and application thereof. Background Art

[0002] At present, the inner tanks of electric water heaters and solar water heaters mostly 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 may occur at the welds. In addition, the material of the enamel inner tank itself is relatively brittle and easily damaged during transportation, so a magnesium rod is needed to protect the inner tank. However, the magnesium rod is 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 peroxide cross-linked polyethylene (PEX a )Rotational molding is used to prepare a steel-plastic composite liner, which has both the pressure-bearing capacity of steel and the properties of PEX a The anti-corrosion performance of the lining does not require magnesium rod protection, and the water quality is better. However, it is currently used for steel-lined rotomolded PEX a The raw materials 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 steel plastic and PEX a The bonding strength between the liners is still low and easy to delaminate; 2) Traditional rotomolded PEX a The peroxide cross-linking agent used in the cross-linking process of the lining will decompose and produce a pungent odor after the cross-linking reaction. 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 water heater inner tank and its preparation method and application. The polyethylene adhesive layer and the heat-resistant organic polymer anti-corrosion layer of the water heater inner tank of the present invention have no irritating odor and can meet the safety and sanitation requirements of bathing water. At the same time, the metal pressure-bearing layer and the polyethylene adhesive layer of the water heater inner tank have strong adhesion, and no delamination will occur during use, thereby meeting the service life requirements of the water heater inner tank.

[0004] In one aspect of the present invention, the present invention provides a water heater inner tank. According to an embodiment of the present invention, the water heater inner tank comprises:

[0005] Metal pressure bearing layer;

[0006] A polyethylene adhesive layer, the polyethylene adhesive layer is arranged on the inner side of the metal pressure-bearing layer, the polyethylene adhesive layer is formed by a polyethylene blend, and the polyethylene blend includes: 80-120 parts by weight of a polyethylene base resin, 2-15 parts by weight of a polar material and 0.1-1 parts by weight of an antioxidant;

[0007] A heat-resistant organic polymer anti-corrosion layer is provided on a side of the polyethylene adhesive layer away from the metal pressure-bearing layer.

[0008] According to the water heater inner tank of the embodiment of the present invention, it is avoided to add a cross-linking agent to the polyethylene adhesive layer, thereby solving the problem in the prior art of PEX a The problem of pungent odor caused by adding peroxide cross-linking agent in the layer is solved, so that the polyethylene adhesive layer meets the hygienic and safety requirements of the water heater inner tank. At the same time, the present invention arranges a heat-resistant organic polymer anti-corrosion layer on the inner side of the polyethylene adhesive layer, and the heat-resistant performance of the heat-resistant organic polymer anti-corrosion layer can meet the use standard of the water heater, and the heat-resistant organic polymer anti-corrosion layer also meets the hygienic and safety requirements of the water heater inner tank. The present invention adopts a polyethylene adhesive layer with good bonding performance as the bonding layer, which is connected between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer, ensuring the bonding strength between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer, and avoiding the delamination phenomenon of the polyethylene adhesive layer and the heat-resistant organic polymer anti-corrosion layer during use. In addition, the present invention adds polar materials to the polyethylene blend, thereby improving the adhesion between the polyethylene adhesive layer and the metal pressure-bearing layer, so that the metal pressure-bearing layer 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 pressure-bearing layer and the polyethylene adhesive layer reaches 285N / cm-380N / cm, and delamination will not occur during use, thereby meeting the service life requirements of the water heater inner tank.

[0009] In addition, the water heater tank according to the above embodiment of the present invention may also have the following additional technical features:

[0010] In some embodiments of the present invention, the material of the heat-resistant organic polymer anti-corrosion layer includes at least one of polypropylene, polybutylene and polycarbonate.

[0011] In some embodiments of the present invention, the thickness ratio of the polyethylene adhesive layer to the heat-resistant organic polymer anti-corrosion layer is (0.5-1.5):(1-2).

[0012] In some embodiments of the present invention, the polyethylene adhesive layer has a thickness of 0.5-1.5 mm.

[0013] In some embodiments of the present invention, the thickness of the heat-resistant organic polymer anti-corrosion layer is 1-2 mm.

[0014] In some embodiments of the present invention, the thickness of the metal pressure-bearing layer is 1-2 mm.

[0015] 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.

[0016] 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.

[0017] In some embodiments of the present invention, the peel strength between the metal pressure-bearing layer and the polyethylene adhesive layer is 285N / cm-380N / cm.

[0018] In another 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:

[0019] (1) Pre-treating the metal pressure-bearing layer;

[0020] (2) placing the polyethylene blend inside the metal pressure-bearing layer, placing the blend in a rotational molding machine, and rotationally molding the blend so as to form a polyethylene adhesive layer inside the metal pressure-bearing layer;

[0021] (3) The material of the heat-resistant organic polymer anti-corrosion layer is loaded into the inner side of the polyethylene adhesive layer, placed in the rotational molding machine, and rotationally molded to form the heat-resistant organic polymer anti-corrosion layer on the inner side of the polyethylene adhesive layer.

[0022] According to the method for preparing the water heater inner tank in the embodiment of the present invention, the polyethylene adhesive layer and the heat-resistant organic polymer anticorrosive layer of the water heater inner tank prepared have no irritating odor and can meet the safety and sanitation requirements of bathing water. At the same time, the metal pressure-bearing layer and the polyethylene adhesive layer of the water heater inner tank 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.

[0023] 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:

[0024] In some embodiments of the present invention, in step (2), the rotational molding temperature is 220° C.-280° C., and the rotational molding time is 15 min-35 min.

[0025] In some embodiments of the present invention, in step (3), the rotational molding temperature is 220° C.-280° C., and the rotational molding time is 15 min-35 min.

[0026] In the third 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 polyethylene adhesive layer and the heat-resistant organic polymer anti-corrosion layer of the water heater inner tank of the water heater have no irritating odor, and can meet the safety and sanitation requirements for bathing water; at the same time, the metal pressure-bearing layer and the polyethylene adhesive layer of the water heater inner tank 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 It is a schematic structural diagram of a water heater inner tank according to an embodiment of the present invention;

[0030] Figure 2 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

[0031] 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.

[0032] In one aspect of the present invention, the present invention provides a water heater inner tank. Figure 1The inner tank of the water heater comprises: a metal pressure-bearing layer 10; a polyethylene adhesive layer 20, which is arranged on the inner side of the metal pressure-bearing layer 10, and the polyethylene adhesive layer 20 is formed by heating a polyethylene blend, and the polyethylene blend comprises: 80-120 parts by weight of a polyethylene basic resin, 2-15 parts by weight of a polar material, and 0.1-1 parts by weight of an antioxidant; a heat-resistant organic polymer anticorrosion layer 30, and the heat-resistant organic polymer anticorrosion layer 30 is arranged on the side of the polyethylene adhesive layer 20 away from the metal pressure-bearing layer 10. Therefore, the present invention avoids adding a cross-linking agent to the polyethylene adhesive layer, thereby solving the problem of generating irritating odor caused by adding a cross-linking agent to the PEX layer in the prior art, and enables the polyethylene adhesive layer to meet the hygienic and safety requirements of the inner tank of the water heater. At the same time, the present invention arranges a heat-resistant organic polymer anticorrosion layer on the inner side of the polyethylene adhesive layer, and the heat-resistant performance of the heat-resistant organic polymer anticorrosion layer can meet the use standard of the water heater, and the heat-resistant organic polymer anticorrosion layer also meets the hygienic and safety requirements of the inner tank of the water heater. The present invention adopts a polyethylene adhesive layer with good bonding performance as the bonding layer, which is connected between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer, thereby ensuring the bonding strength between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer, and avoiding the delamination phenomenon between the polyethylene adhesive layer and the heat-resistant organic polymer anti-corrosion layer during use. In addition, the present invention adds polar materials to the polyethylene blend, improves the bonding between the polyethylene adhesive layer and the metal pressure-bearing layer, so that the metal pressure-bearing layer 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, so that the peel strength between the metal pressure-bearing layer and the polyethylene adhesive layer reaches 285N / cm-380N / cm, and no delamination phenomenon will occur during use, thereby meeting the service life requirements of the water heater tank.

[0033] The principle by which the water heater tank proposed by the present invention can achieve the above beneficial effects is described in detail below:

[0034] In the prior art, peroxide cross-linked polyethylene (PEX a )Rotational molding is used to prepare a steel-plastic composite liner, which has both the pressure-bearing capacity of steel and the properties of PEX a The anti-corrosion performance of the lining. aDuring the formation of the lining, since the heat resistance of the polyethylene basic resin does not meet the use standards of the water heater, a cross-linking agent is required to promote the polyethylene basic resin to undergo a cross-linking reaction under certain conditions to form a cross-linked polyethylene lining. In this field, a peroxide system cross-linking agent is generally used. The cross-linking agent will decompose and produce a pungent odor after the heating reaction. For example, DCP is easily decomposed into gases such as acetophenone, methane, and 2-phenylisopropanol. In particular, acetophenone can cause severe irritation to the human eyes or respiratory tract, and BIBP is easily decomposed into vapors 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.

[0035] In order to solve the above technical problems, the present invention avoids adding a crosslinking agent to the polyethylene adhesive layer, thereby solving the problem in the prior art of adding a crosslinking agent to the polyethylene adhesive layer. a The problem of pungent odor caused by adding a cross-linking agent to the layer is solved, so that the polyethylene adhesive layer meets the sanitary and safety requirements of the water heater inner tank. At the same time, in order to solve the problem that the heat resistance of the polyethylene basic resin does not meet the use standard of the water heater, the present invention arranges a heat-resistant organic polymer anti-corrosion layer on the inner side of the polyethylene adhesive layer. The long-term temperature resistance of the heat-resistant organic polymer anti-corrosion layer reaches 95°C, which meets the requirement of long-term use at 80-85°C, and its heat resistance can meet the use standard of the water heater. The heat-resistant organic polymer anti-corrosion layer plays a role in blocking water from penetrating and contacting the metal pressure-bearing layer, providing better anti-corrosion performance for metal parts. In addition, no cross-linking agent is used in the heat-resistant organic polymer anti-corrosion layer, and there is no pungent odor problem caused by the cross-linking agent. Therefore, the heat-resistant organic polymer anti-corrosion layer also meets the sanitary and safety requirements of the water heater inner tank. However, the adhesion between the heat-resistant organic polymer anti-corrosion layer and the metal pressure-bearing layer is poor. In order to solve this problem, the present invention adopts a polyethylene adhesive layer with good bonding properties as the adhesive layer, which is connected between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer, thereby ensuring the bonding strength between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer and avoiding delamination of the polyethylene adhesive layer and the heat-resistant organic polymer anti-corrosion layer during use.

[0036] In order to further ensure the bonding strength between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer, the present invention adds a polar material to the polyethylene blend. The polar material contains polar groups. The polar groups in the polar material can react with the hydroxyl groups on the metal pressure-bearing layer to generate chemical bonds, thereby improving the bonding between the polyethylene adhesive layer and the metal pressure-bearing layer. The metal pressure-bearing layer only needs to undergo a simple degreasing step, without the need for complicated sandblasting, pickling, phosphating, etc., to achieve the bonding strength required for use. The peel strength between the metal pressure-bearing layer and the polyethylene adhesive layer reaches 285N / cm-380N / cm, and delamination will not occur during use, thereby meeting the service life requirements of the water heater inner tank.

[0037] In the embodiments of the present invention, the material of the above-mentioned heat-resistant organic polymer anti-corrosion layer is not particularly limited, as long as its heat resistance and sanitary and safety performance can meet the use standards of the water heater inner tank. According to some specific embodiments of the present invention, the material of the heat-resistant organic polymer anti-corrosion layer includes at least one of polypropylene, polybutylene and polycarbonate. The heat-resistant organic polymer anti-corrosion layer formed by the above-mentioned types of materials can not only meet the use standards of the water heater inner tank for heat resistance, but also meet the sanitary and safety requirements of the water heater inner tank.

[0038] According to some further specific embodiments of the present invention, the thickness ratio of the polyethylene adhesive layer to the heat-resistant organic polymer anti-corrosion layer can be (0.5-1.5):(1-2), thereby further ensuring the bonding strength between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer, and further avoiding delamination between the metal pressure-bearing layer and the heat-resistant organic polymer anti-corrosion layer.

[0039] As some specific examples, the thickness of the polyethylene adhesive layer can be 0.5-1.5 mm (for example, 0.5 / 0.7 / 0.9 / 1.0 / 1.2 / 1.3 / 1.5 mm). As some specific examples, the thickness of the heat-resistant organic polymer anticorrosive layer can be 1-2 mm (for example, 1 / 1.2 / 1.4 / 1.6 / 1.8 / 2 mm). As some specific examples, the thickness of the metal pressure-bearing layer can be 1-2 mm (for example, 1 / 1.2 / 1.4 / 1.6 / 1.8 / 2 mm).

[0040] In the embodiments of the present invention, the specific types of the above-mentioned 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 the hydroxyl groups on the metal pressure-bearing layer to form chemical bonds, thereby improving the adhesion between the PE liner and the metal pressure-bearing layer. 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 the hydroxyl groups on the metal pressure-bearing layer to form chemical bonds, thereby improving the adhesion between the polyethylene adhesive layer and the metal pressure-bearing layer. The grafting rate on the polyolefin is also not particularly limited, and is generally selected between 1% and 10%.

[0041] In an embodiment of the present invention, the antioxidant is used to prevent the polyethylene adhesive layer from oxidative aging. The specific type of the 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)propionic acid]pentaerythritol ester and 4,4'-thiobis(6-tert-butyl-3-methyl)phenol.

[0042] In the embodiment of the present invention, the specific material of the metal pressure-bearing layer is not particularly limited, and may be, for example, a carbon steel pressure-bearing layer.

[0043] In another aspect of the present invention, the present invention provides a method for preparing the above-mentioned water heater inner tank. Figure 2 , the method comprising:

[0044] S100: pre-treating the metal pressure-bearing layer.

[0045] In this step, the metal pressure-bearing layer is pretreated to remove oil stains and rust on the surface of the metal pressure-bearing layer so that the polyethylene adhesive layer can be better bonded to the metal pressure-bearing layer.

[0046] S200: The polyethylene blend is loaded into the inner side of the metal pressure-bearing layer, placed in a rotational molding machine, and rotationally molded to form a polyethylene bonding layer on the inner side of the metal pressure-bearing layer.

[0047] According to some specific embodiments of the present invention, in this step, the rotational molding temperature can be 220°C-280°C (for example, it can be 220 / 230 / 240 / 250 / 260 / 270 / 280°C, etc.), the rotational molding time can be 15min-35min (for example, it can be 15 / 20 / 25 / 30 / 35min), and then the inner liner is cooled.

[0048] Before the polyethylene blend is loaded into the inner side of the metal pressure-bearing layer, the polyethylene base resin, polar material and antioxidant are first melt-blended at 130-150° C. (for example, melt-blended in a twin-screw extruder), and then granulated to obtain the polyethylene blend.

[0049] S300: The material of the heat-resistant organic polymer anti-corrosion layer is loaded into the inner side of the polyethylene adhesive layer, placed in a rotational molding machine, and rotationally molded to form the heat-resistant organic polymer anti-corrosion layer on the inner side of the polyethylene adhesive layer.

[0050] According to some specific embodiments of the present invention, in this step, the rotational molding temperature can be 220°C-280°C (for example, it can be 220 / 230 / 240 / 250 / 260 / 270 / 280°C, etc.), the rotational molding time can be 15min-35min (for example, it can be 15 / 20 / 25 / 30 / 35min), and then the inner liner is cooled.

[0051] According to the method for preparing the water heater inner tank in the embodiment of the present invention, the polyethylene adhesive layer and the heat-resistant organic polymer anticorrosive layer of the water heater inner tank prepared have no irritating odor and can meet the safety and sanitation requirements of bathing water. At the same time, the metal pressure-bearing layer and the polyethylene adhesive layer of the water heater inner tank 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.

[0052] In the third 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 polyethylene adhesive layer and the heat-resistant organic polymer anti-corrosion layer of the water heater inner tank of the water heater have no irritating odor, and can meet the safety and sanitation requirements for bathing water; at the same time, the metal pressure-bearing layer and the polyethylene adhesive layer of the water heater inner tank 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.

[0053] Specifically, the water heater may be an electric water heater, a solar water heater or the like.

[0054] 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.

[0055] Example 1

[0056] This embodiment provides a water heater inner tank, and the preparation method thereof includes:

[0057] 1) 80 g of linear low-density polyethylene LLDPE1802, 5 g of unsaturated polyester resin HS8706, and 0.1 g of antioxidant Irganox 1010 were extruded into pellets and ground into powder by a twin-screw extruder at 140° C. and 75 rpm to obtain a polyethylene blend.

[0058] 2) Degreasing and rust removal of the carbon steel welded liner with a thickness of 1.4 mm.

[0059] 3) The polyethylene blend is loaded into the inner side of the carbon steel pressure-bearing layer, 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 polyethylene bonding layer with a thickness of 1.5 mm on the inner side of the carbon steel pressure-bearing layer.

[0060] 4) The polypropylene powder is loaded into the inner side of the polyethylene adhesive layer, 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 heat-resistant organic polymer anticorrosive layer with a thickness of 2 mm on the inner side of the polyethylene adhesive layer.

[0061] Example 2

[0062] This embodiment provides a water heater inner tank, and the preparation method thereof includes:

[0063] 1) 120 g of linear low-density polyethylene LLDPE1802, 8 g of epoxy resin E12 and 0.8 g of antioxidant Irganox1010 were extruded into pellets and ground into powder by a twin-screw extruder at 140° C. and 75 rpm to obtain a polyethylene blend.

[0064] 2) Degreasing and rust removal of the carbon steel welded liner with a thickness of 1.5 mm.

[0065] 3) The polyethylene blend is loaded into the inner side of the carbon steel pressure-bearing layer, 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 polyethylene bonding layer with a thickness of 1.2 mm on the inner side of the carbon steel pressure-bearing layer.

[0066] 4) The polybutene powder is loaded into the inner side of the polyethylene adhesive layer and placed in a rotational molding machine for rotational molding. 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 heat-resistant organic polymer anticorrosive layer with a thickness of 1.8 mm on the inner side of the polyethylene adhesive layer.

[0067] Example 3

[0068] This embodiment provides a water heater inner tank, and the preparation method thereof includes:

[0069] 1) 100 g of linear low-density polyethylene LLDPE1802, 10 g of epoxy resin E12 and 0.5 g of antioxidant Irganox1010 were extruded into pellets and ground into powder by a twin-screw extruder at 140° C. and 75 rpm to obtain a polyethylene blend.

[0070] 2) The carbon steel welded liner with a thickness of 1.65 mm was degreased and derusted.

[0071] 3) The polyethylene blend is loaded into the inner side of the carbon steel pressure-bearing layer, 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 polyethylene bonding layer with a thickness of 1 mm on the inner side of the carbon steel pressure-bearing layer.

[0072] 4) The polycarbonate powder is loaded into the inner side of the polyethylene adhesive layer and placed in a rotational molding machine for rotational molding. 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 heat-resistant organic polymer anticorrosive layer with a thickness of 2 mm on the inner side of the polyethylene adhesive layer.

[0073] Example 4

[0074] This embodiment provides a water heater inner tank, and the preparation method thereof includes:

[0075] 1) 100 g of linear low-density polyethylene LLDPE1802, 8 g of maleic anhydride grafted polyolefin MA-LLDPE (grafting rate of 1.2 wt%), and 0.1 g of antioxidant Irganox 1010 were extruded into granules and ground into powder by a twin-screw extruder at 140° C. and 75 rpm to obtain a polyethylene blend.

[0076] 2) Degreasing and rust removal of the carbon steel welded liner with a thickness of 1.8 mm.

[0077] 3) The polyethylene blend is loaded into the inner side of the carbon steel pressure-bearing layer, 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 polyethylene bonding layer with a thickness of 1.2 mm on the inner side of the carbon steel pressure-bearing layer.

[0078] 4) The polypropylene powder is loaded into the inner side of the polyethylene adhesive layer, placed in a rotational molding machine, and rotationally molded. The rotational molding temperature is 230°C, the heating time is 25 minutes, and the cooling time is 15 minutes, so as to form a heat-resistant organic polymer anticorrosive layer with a thickness of 1.5 mm on the inner side of the polyethylene adhesive layer.

[0079] Comparative Example 1

[0080] 1) 100 g of linear low-density polyethylene LLDPE1802, 1 g of peroxide crosslinking agent DCP, 10 g of epoxy resin E12, and 0.5 g of antioxidant Irganox 1010 were extruded into granules and ground into powder by a twin-screw extruder at 140° C. and 75 rpm to obtain a crosslinkable polyethylene blend.

[0081] 2) Degrease and rust the carbon steel welded liner.

[0082] 3) The cross-linkable polyethylene blend is loaded into the inner side of the carbon steel pressure-bearing layer and placed in a rotational molding machine for rotational molding. The rotational molding temperature is 230°C, the heating time is 25 minutes, and the cooling time is 15 minutes, so as to form PEX inside the carbon steel pressure-bearing layer. a Lining layer.

[0083] Comparative Example 2

[0084] In this comparative example, epoxy resin E12 is not added, and other contents are the same as those in Example 3.

[0085] According to GB / T23257-2017, the peel strength (N / cm) of the composite anti-corrosion layer (i.e., polyethylene adhesive layer and heat-resistant organic polymer anti-corrosion layer) of Examples 1-4 and Comparative Examples 1-2 peeled off from the carbon steel pressure-bearing layer is measured. The test method is as follows: scratch a 1 cm wide strip on the composite anti-corrosion layer of the liner product, the length is greater than 20 cm, and the scratch depth reaches the metal part. Peel off one end of the strip from the metal part by at least 2 cm, and use a tensile testing machine to pull up the peeled strip at a speed of 10 mm / min; read the stress value of the tensile testing machine, and after the tension stabilizes, take the average value after stabilization as the peel strength.

[0086] 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 smell. 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 1.

[0087] Table 1

[0088]

[0089] It can be seen from Table 1 that the peel strength of Examples 1-4 is all above 289.5 N / cm, the odor N0 of the liner just produced is all below 1.5 level, and the odor Ng after being placed in the air for 24 hours is 24 All are below 1.3 level, and the odor after being placed in the air for 48 hours is Ng 48 All are below 1.2 level, and the odor after water treatment is N w All are below level 1.1, meeting the hygiene and safety requirements for the water heater inner tank.

[0090] Compared with Comparative Example 1, the odor of the liner prepared in Example 3 is significantly reduced in various states, which shows that the odor is significantly reduced after avoiding the addition of the cross-linking agent in Example 3.

[0091] Compared with Comparative Example 2, the peel strength of the polyethylene adhesive layer prepared in Example 3 is significantly improved. It can be seen that the addition of polar materials significantly improves the peel strength of the polyethylene adhesive layer, meeting the service life requirements of the water heater tank.

[0092] 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.

[0093] 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 water heater tank, characterized in that: include: Metal pressure bearing layer; A polyethylene adhesive layer, the polyethylene adhesive layer is arranged on the inner side of the metal pressure-bearing layer, the polyethylene adhesive layer is formed by a polyethylene blend, and the polyethylene blend includes: 80-120 parts by weight of a polyethylene base resin, 2-15 parts by weight of a polar material and 0.1-1 parts by weight of an antioxidant; A heat-resistant organic polymer anti-corrosion layer is provided on a side of the polyethylene adhesive layer away from the metal pressure-bearing layer.

2. The water heater inner tank according to claim 1, characterized in that: The material of the heat-resistant organic polymer anti-corrosion layer includes at least one of polypropylene, polybutylene and polycarbonate.

3. The water heater inner tank according to claim 1, characterized in that: The thickness ratio of the polyethylene adhesive layer to the heat-resistant organic polymer anti-corrosion layer is (0.5-1.5):(1-2).

4. The water heater inner tank according to claim 3, characterized in that: The thickness of the polyethylene adhesive layer is 0.5-1.5 mm.

5. The water heater inner tank according to claim 4, characterized in that: The thickness of the heat-resistant organic polymer anti-corrosion layer is 1-2 mm.

6. The water heater inner tank according to claim 5, characterized in that: The thickness of the metal pressure-bearing layer is 1-2 mm.

7. The water heater inner tank 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 water heater inner tank 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. The water heater inner tank according to any one of claims 1 to 6, characterized in that: The peel strength between the metal pressure-bearing layer and the polyethylene adhesive layer is 285N / cm-380N / cm.

10. A method for preparing a water heater tank according to any one of claims 1 to 9, characterized in that: include: (1) Pretreatment of the metal pressure-bearing layer; (2) placing the polyethylene blend inside the metal pressure-bearing layer, placing the blend in a rotational molding machine, and rotationally molding the blend so as to form a polyethylene adhesive layer inside the metal pressure-bearing layer; (3) The material of the heat-resistant organic polymer anti-corrosion layer is loaded into the inner side of the polyethylene adhesive layer, placed in the rotational molding machine, and rotationally molded to form the heat-resistant organic polymer anti-corrosion layer on the inner side of the polyethylene adhesive layer.

11. The method according to claim 10, characterized in that In step (2), the rotational molding temperature is 220° C.-280° C., and the rotational molding time is 15 min-35 min.

12. The method according to claim 10, characterized in that In step (3), the rotational molding temperature is 220°C-280°C, and the rotational molding time is 15min-35min.

13. A water heater, characterized in that: A water heater inner tank according to any one of claims 1 to 9 or a water heater inner tank prepared by the method according to any one of claims 10 to 12.

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