CN116082831A - PA6 material with excellent adhesive force and suitable for double-color injection molding oil valve assembly - Google Patents

Abstract

The invention provides a PA6 material with excellent adhesive force, which is suitable for double-shot molding of an oil valve assembly. Comprising PA6 resin with aromatic dibasic acid as end capping agent and conventional auxiliary agent. The oil valve component with excellent adhesion force can be obtained through double-shot injection molding with polyolefin materials, and firm sealing assembly with the plastic fuel tank shell materials is realized through welding molding, so that the fuel oil permeation quantity is greatly reduced. Is especially suitable for the components such as a one-way valve, a gravity valve, a refueling limit valve and the like of the plastic fuel tank filler.

Description

PA6 material with excellent adhesive force and suitable for double-color injection molding oil valve assembly

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a PA6 material with excellent adhesive force and suitable for double-shot injection molding of an oil valve component and a preparation method thereof.

Background

Fuel tanks are important components of automobiles, are used for storing fuel oil, and are made of light plastics instead of metal materials, so that the fuel tanks have important significance for the weight reduction of automobiles. Compared with a metal fuel tank, the metal fuel tank has the excellent performances of light weight, large freedom of shape design, high space utilization rate, good corrosion resistance, easiness in processing and forming, low heat conductivity, good low-temperature impact resistance and the like.

Because the chemical structure of polyethylene is similar to that of fuel oil and is aliphatic hydrocarbon, and the polyethylene has compatibility, when the polyethylene is used as a fuel tank, the fuel oil can be permeated and diffused to the outside through the inner wall to be gasified and lost, namely, the barrier property of the polyethylene to the effective components of the fuel oil is lower, so that the early polyethylene fuel tank is replaced by a nylon fuel tank which appears later, and the development of years and the continuous perfection of emission regulations are carried out, so that the gasoline plastic fuel tank in China generally adopts a multilayer blow molding coextrusion process at present. The outer layer and the inner layer are made of High Density Polyethylene (HDPE), and the barrier layer is made of ethylene vinyl alcohol copolymer (EVOH). The fuel permeation value of this type of plastic fuel tank may be below 10mg/24h. However, in order to meet the functional requirements of fuel filling, ventilation, safety in overturning, placement of an oil pump and the like, the fuel tank necessarily comprises a refueling check valve, a gravity valve, a refueling limit valve, an oil pump mounting structure and the like. These oil valve assemblies are commonly sealed with openings, penetration welds, and the like. In view of the adhesion with the fuel tank housing material (HDPE), the material of the welded component is generally HDPE, but the fuel barrier property is low, and the fuel vapor escapes through the open welded component of the fuel tank, and the fuel permeation value increases to 300 to 500mg/24h. Therefore, the number of openings in the surface of the fuel tank and the fuel barrier capability of the welded component are major factors affecting the evaporative emission level thereof.

Referring to the design experience of the LEV lI standard in California, the fuel tank evaporative emissions index is typically set below 100mg/24h, generally between 60 and 80mg/24 h. Therefore, it is necessary to use a PA6 material having a low fuel permeation coefficient (10 mg/24 h) instead of a HDPE material having a high fuel permeation coefficient (500 mg/24 h) as a welding member material. Furthermore, in order to meet the welding strength requirement with the fuel tank shell material (HDPE), the PE material is suitable to be used as an adhesion transition layer, so that the PA6/PE double-shot injection molding fuel valve assembly becomes a better welding part material scheme.

The double-color injection molding is mainly to obtain a product by matching two material pipes of a double-color molding machine with two sets of dies and performing twice molding according to the sequence. Simple and easy, the mill that does not possess two material pipe injection molding machine can select the PE material adhesive linkage of shaping simple structure earlier, then put into the mould as the inserts, again the PA6 material carries out the injection molding, forms holistic oil valve subassembly goods.

In order to ensure that the welded part can meet the functional requirements of fuel filling, ventilation, overturning safety, oil pump arrangement and the like, the welded oil valve assembly is required to bear the external thrust of more than 500N without loosening, namely the material adhesion force. PA6/PE is an incompatible system, and if PA6 is modified with a maleic anhydride-and carboxylic acid-based compatibilizer, the fuel permeation coefficient of PA6 is significantly improved, which is clearly contrary to the original purpose. Currently, improving the adhesion of PA6/PE bi-color injection molded parts generally depends on injection molding plant optimization process and host machine plant optimization design: such as the proposal of raising the mold temperature and the injection molding processing temperature, preheating the insert before secondary injection molding, and enlarging the contact surface of the product design sawtooth groove. The proposal of the material end has not been reported.

Disclosure of Invention

In order to solve the problems, the invention provides the PA6 material with excellent adhesive force, which is suitable for double-shot injection molding of an oil valve component, and the corresponding relation of special characteristic indexes of synthetic end raw materials to special purposes of a terminal is identified, and the melting point and mechanical properties of the material are not influenced by regulating and controlling a blocking agent, so that the PA6 resin with excellent adhesive force can be obtained, and a solution of a material end is provided for customers (injection molding plants).

In order to achieve the above purpose, the invention adopts the following technical scheme:

the PA6 material with excellent adhesive force suitable for the double-shot injection molding oil valve assembly comprises the following components in parts by weight:

50-100 parts of PA6 resin with aromatic dibasic acid as end capping agent

0-50 parts of reinforcing material

0.5-2 parts of conventional auxiliary agent

The aromatic dibasic acid is one or more of terephthalic acid, phthalic acid or isophthalic acid; the melting point of the PA6 resin taking the aromatic dibasic acid as the end capping agent is 220 ℃, and the viscosity is 2.0-3.0.

The reinforcing material can be selected from glass fiber, carbon fiber, glass microsphere, magnesium sulfate whisker, talcum powder, wollastonite, calcium carbonate and the like;

the conventional auxiliary agents comprise an antioxidant, a light stabilizer, a heat stabilizer, a lubricant, a colorant and the like.

Compared with the prior art, the invention has the following beneficial effects:

1) The invention can meet the special field application through simple customization, only the end capping agent is required to be regulated and controlled, other polymerization processes are not required to be changed, the melting point is not reduced, the PA6 resin with excellent adhesion force can be obtained, the invention is suitable for double-color injection molding of the oil valve component, the adhesion force of the double-color injection molding joint surface is strong, and the welding force of the oil valve component and the fuel tank is strong.

2) According to the invention, through research and recognition of the interrelationships of materials, processes and parts, the corresponding relation of special characteristic indexes of the synthetic end raw materials to special purposes of the terminal is identified, and a thought reference is provided for developing customized solutions in the industry upstream and downstream.

Drawings

FIG. 1 is a schematic illustration of a PA6/PE bi-color injection molded tensile bar according to the present invention;

FIG. 2 is a schematic illustration of a PA6/PE bi-injection molded oil valve assembly and fuel tank housing of the present invention.

Detailed Description

In order to make the technical scheme of the invention clearer and more definite, the invention is further described below, and any scheme obtained by carrying out equivalent substitution and conventional reasoning on the technical characteristics of the technical scheme of the invention falls into the protection scope of the invention. The materials used in the invention are all conventional and commercially available.

Example 1

1) Preparation of PA6 resin: caprolactam, aminocaproic acid and 0.5% terephthalic acid were polymerized, extracted and dried to give PA6, whose relative viscosity was measured at 2.42, melting point 220 ℃.

2) Preparing a PA6 composite material: 98.5 parts of PA6 from step 1) were mixed with 0.5 part of N54/1033, 0.5 part of OP wax, 0.3 part of H318 and pelletized in a twin-screw extruder at 250℃and at 480rpm.

3) PA6/PE bicolor injection molding tensile sample bar: firstly, forming a PE half-root tensile spline, then placing the PE half-root tensile spline into a die as an insert, and then performing injection molding on the PE half-root tensile spline by using a PA6 composite material to form an integral tensile spline (shown in figure 1).

4) PA6/PE double-shot molding oil valve product: putting the PA6 composite material into a first material pipe of a double-color forming machine, and injecting and forming a main body of the end cover of the product; turning over the die; and (5) putting PE into a second material pipe of the bicolor forming machine, and injecting and forming the residual circular ring part of the product.

Example 2

69 parts of PA6 resin prepared in example 1, 0.5 part of N54/1044, 0.3 part of calcium stearate, 0.2 part of antioxidant 1098 and 0.2 part of antioxidant 168 are mixed, fed from a twin-screw extruder, fed from 30 parts of glass fiber side, and granulated. The other steps are the same as in example 1.

Example 3

The difference from example 2 is the difference in the number of glass fibers and the PA6 content is correspondingly reduced.

Example 4

The difference from example 2 is that the reinforcing material is fed from the main feed by glass fibers instead of wollastonite.

Example 5

Caprolactam, aminocaproic acid and 1% terephthalic acid were polymerized, extracted and dried to give PA6, whose relative viscosity was measured for 2.81, melting point 220 ℃. The other steps are the same as in example 2.

Example 6

Caprolactam, aminocaproic acid and 0.5% isophthalic acid were polymerized, extracted and dried to give PA6, whose relative viscosity was measured for 2.29, melting point 220 ℃. The other steps are the same as in example 2.

Example 7

Step 3) PA6/PE bicolor injection molding stretching spline: firstly, a half tensile spline is molded by using a PA6 composite material, then the half tensile spline is put into a die as an insert, and then injection molding is carried out by using a PE material to form an integral tensile spline. The other steps are the same as in example 2.

Example 8

Step 4) PA6/PE double-shot molding oil valve product: putting PE into a second material pipe of the bicolor forming machine, and injecting and forming a circular ring part of the product; turning over the die; and (3) putting the PA6 composite material into a first material pipe of a double-color forming machine, and injecting and forming the end cover main body of the product. The other steps are the same as in example 2.

Comparative example 1

Caprolactam, aminocaproic acid and 1% adipic acid were polymerized, extracted and dried to give PA6, which was checked for relative viscosity of 2.41, melting point 220 ℃. The other steps are the same as in example 2.

Comparative example 2

The difference from comparative example 1 is that the content of the toughening agent N413A and PA6 is correspondingly reduced by adding 5 parts.

Comparative example 3

The difference from comparative example 1 is that 0.5 part of calcium chloride was added and the PA6 content was correspondingly reduced.

Comparative example 4

Caprolactam, aminocaproic acid and 0.5% of sebacic acid are polymerized, extracted and dried to obtain PA6, the relative viscosity of which is detected to be 2.78, and the melting point of which is 220 ℃. The other steps are the same as in comparative example 1.

The product performance testing method comprises the following steps:

(1) Crystallization temperature: DSC 822 type, temperature rising rate of 10 ℃/min;

(2) Tensile strength: according to ISO 527 method, the spline size is 170 x 10 x 4mm, the test speed is 5mm/min;

(3) Tensile load of PA6/PE bicolor injection molding sample bar: a universal material tester (shown in figure 1) with spline sizes of 170 x 10 x 4mm and test speeds of 50mm/min;

(4) Oil valve product thrust experiment: the A6/PE double-color injection molding oil valve product is welded on a multi-layer blow molding co-extrusion material fuel tank (as shown in figure 2) through rotation, and a transverse thrust loading experiment is carried out according to the enterprise standard;

(5) Fuel permeation value of assembly: and is carried out according to the enterprise standard.

Table 1 results of performance tests for examples and comparative examples

The embodiment shows that the PA6 material provided by the invention has excellent adhesion after double-color injection molding with PE material without affecting the melting point and mechanical property of the material, and the tensile load of the PA6/PE double-color injection molding sample strip is obviously improved. After the oil valve product is welded with an oil tank, the test thrust experiment is qualified, the functional requirements of fuel filling, ventilation, turnover safety, oil pump arrangement and the like are met, the fuel permeation value of the assembly is less than 80mg/24h, and the design is superior to the design of the LEV II standard in California.

As can be seen from the comparative examples, due to the differences of thermal conductivity, specific heat capacity and the like of the materials, the heat dissipation rate is uneven, the heat dissipation transition difference between PE and PA6 is large, the shrinkage and crystallization of the materials are uneven, defects are easy to generate, and the interface adhesion is poor. And, although some auxiliary agents have an improving effect, other risks such as chemical stress concentration, melting point and mechanical property change are brought about.

The above description is merely an embodiment of the present invention, but the scope of the present invention is not limited thereto.

Claims (4)

1. The PA6 material with excellent adhesive force suitable for the double-shot injection molding oil valve assembly is characterized by comprising the following components in parts by weight:

50-100 parts of PA6 resin with aromatic dibasic acid as a blocking agent;

0-50 parts of reinforcing material;

0.5-2 parts of conventional auxiliary agent.

2. The PA6 material excellent in adhesion suitable for a two-shot injection molding oil valve assembly according to claim 1, characterized in that: the aromatic dibasic acid is one or more of terephthalic acid, phthalic acid or isophthalic acid; the melting point of the PA6 resin taking the aromatic dibasic acid as the end capping agent is 220 ℃, and the viscosity is 2.0-3.0.

3. The PA6 material excellent in adhesion suitable for a two-shot injection molding oil valve assembly according to claim 1, characterized in that: the reinforcing material is selected from glass fiber, carbon fiber, glass microsphere, magnesium sulfate whisker, talcum powder, wollastonite and calcium carbonate.

4. The PA6 material excellent in adhesion suitable for a two-shot injection molding oil valve assembly according to claim 1, characterized in that: the conventional auxiliary agents comprise an antioxidant, a light stabilizer, a heat stabilizer, a lubricant and a colorant.

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