Method for molding disposable container, and container molded by means of same

Abstract

Provided in the present invention creation is a method for molding a disposable container, the method comprising the steps of: injection molding an inner layer component of a container; injection molding an outer layer component of the container; performing primary mold opening and nitrogen physical foaming; and performing secondary mold opening, so as to eject the molded container product, etc. In the method for molding a container provided in the present invention creation, the inner layer of the container and a food contact layer are molded by using a raw polymer material, such that same adequately comply with food contact safety standards; and the outer layer is molded by using a recycled polymer material, and a nitrogen physical foaming process is used during the molding process, such that compared with similar products, the product weight is reduced by about 40% and the thermal insulation of the product is increased by about 30%. In addition, the two-component double-layer molding process further endows the container product with good sealing properties.

Description

Method for forming disposable container and container formed by the method TECHNICAL FIELD

[0001] The present invention relates to the field of food-grade foamed plastic products, in particular to a method for forming a disposable container and a container formed by the method. BACKGROUND

[0002] In daily life, commonly used food-grade disposable containers are usually paper cups or disposable polypropylene cups. The former is usually a paper shell with a plastic material lining (such as low-density polyethylene, LDPE), which is difficult to separate in recycling due to two different raw materials, and the paper cup has a seam in processing, which causes the container to be difficult to seal. The latter is usually made of porous polymer materials (such as polypropylene), which also forms a seam in processing, and the wall thickness of the disposable polypropylene cup is limited, which is not conducive to heat insulation, and usually requires an additional cup sleeve, such as increasing the wall thickness of the container, which requires an increase in the amount of raw materials, which is not conducive to cost control and also increases the amount of plastic materials, which is not conducive to environmental protection.

[0003] A foamed disposable plastic container has appeared on the market, which is made of a single-color single-component material by a micro-foaming process, but has the problem of high raw material cost. In order to save costs, the industry usually uses recycled materials as raw materials for preparing the container body, but the contact between food or beverage and the container body made of recyclable materials poses a food safety risk.

[0004] Therefore, a new process must be provided to solve the problems of sealing, heat insulation, environmental protection and food safety of disposable containers from the source of manufacturing. TECHNICAL PROBLEM

[0005] The present invention provides a method for forming a container by a micro-foaming process of a double-color double-component material, which uses virgin polymer material as raw material to form the inner surface of the container and the part in contact with the human mouth, and uses recycled polymer material to form the other parts of the container, thereby improving the sealing and heat insulation performance of the disposable plastic container, the virgin material provides excellent food safety performance to the disposable container, and the use of recycled material reduces the amount of virgin material, reduces carbon emissions, and is more friendly to the environment. TECHNICAL SOLUTION

[0006] To achieve the above purpose, the present invention provides a method for forming a disposable container, comprising the following steps:

[0007] Take virgin polymer material, inject it into the first shot cavity of the double-component mold from the first shot of the double-component injection molding machine, and injection mold the inner layer part of the container;

[0008] Rotating the two-component mold 180 degrees, rotating the formed container inner layer piece to the second injection cavity of the two-component mold, and closing the mold;

[0009] Taking the same regenerated polymer mixture as the virgin polymer, injecting the second injection cavity of the two-component mold from the second injection station of the two-component injection molding machine, and injection molding the container outer layer piece; filling the physical foaming nitrogen gas while the injection station melts the material;

[0010] Once the mold is opened, the container outer layer piece and the container inner layer piece are fixed on the back mold of the mold, the mold blowing cooling system is started, the container outer layer piece is moved to the mold cavity position of the required physical microcellular foaming surface with the back mold, and the mold temperature control system is controlled to foam the container outer layer piece to the pre-set wall thickness with nitrogen gas;

[0011] The second time the mold is opened, the formed container is ejected.

[0012] In the above molding method, the regenerated polymer mixture includes 10% to 30% by weight of polymer nucleated by Borealis nucleation technology (i.e., BNT nucleation), and 70% to 90% by weight of regenerated polymer.

[0013] In the above molding method, the weight ratio of the virgin polymer to the regenerated polymer mixture is [1:3] to [1:2].

[0014] In the above molding method, the polymer is polyethylene or polypropylene.

[0015] In the above molding method, the melt flow index of the polypropylene is 50 to 100.

[0016] In the above molding method, the wall thickness of the container inner layer piece is 0.3mm to 0.5mm.

[0017] In the above molding method, the initial wall thickness of the container outer layer piece is 0.5mm to 0.8mm, and the foaming thickness is 2 to 6 times the initial thickness.

[0018] In the above molding method, the injection speed of the first injection station and the second injection station is 300mm / s to 500mm / s.

[0019] In the above molding method, the molding temperature is 190℃ to 215℃, the temperature of the front mold of the mold is 70℃ to 80℃, and the temperature of the back mold is 40℃ to 50℃.

[0020] In the above molding method, the filling pressure of the injection molding is 80bar to 100bar, and the injection speed is 70% to 80%.

[0021] The forming method further includes a step of applying product information to the outer surface of the container outer layer after foaming.

[0022] In the forming method, the product information includes production batch, serial number, material, color, and / or material formula of the product.

[0023] In the forming method, the product information is a two-dimensional code integrated with the product information, which is engraved by digital ultraviolet laser.

[0024] The application further provides a disposable container formed by the forming method. Advantages

[0025] The forming process of the two-component two-color microcellular foaming container provided by the application forms the inner layer and the food contact layer using virgin polymer materials, so that the container has excellent food contact safety standards, and forms the outer layer using recycled polymer materials; the two-component two-layer forming process also gives the container good sealing performance, and the container remains normal when containing liquid at a temperature of -4°C to 99°C; the use of nitrogen physical foaming process in the forming process also reduces the product weight by about 40%, and the use of BNT nucleation microcellular gas wrapped recycled polymer materials increases the heat insulation of the product by about 30%. The two-dimensional code containing product information is engraved on the outer surface of the container by laser, so that each container product has unique identity information, which can be accurately identified and recycled by cooperating with special recycling equipment, and the material can be accurately recycled according to the information such as the material type, product color, and production batch of the container product, thereby improving the efficiency of recycling and regeneration, reducing the loss of raw materials, and reducing carbon emissions. BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a process flow diagram of the forming method of the disposable container provided by the application;

[0027] FIG. 2 is a partial cross-sectional view of the container provided by the application. DETAILED DESCRIPTION

[0028] The present invention provides a molding method for one-time molding of a two-component two-color product of a two-component BNT nucleation technology polymer material and a physical nitrogen microcellular foaming molten plastic composition, mainly for two-component two-color microcellular foaming molded food containers involving food packaging. In the method of the present invention, in the first part, the inner layer region of the container in direct contact with food is injection molded using a virgin food-grade polymer, and then the mold is rotated by 180 degrees; in the second part, the outer layer region of the container not in direct contact with food is injection molded using PCR (post consumer recycled) recycled polymer added with 10% to 30% BNT nucleation polymer, and nitrogen gas is filled as a gas dissolved in the polymer in the injection and glue melting step to form microcellular polymer filled in the mold cavity for the first time by wrapping the gas with BNT nucleation polymer to form microcellular pores; then the mold opening stroke is controlled to be 5mm to 30mm distance and the mold temperature is controlled to maintain the product in the mold for the second time of physical microcellular foaming; then the mold is opened again and the product is ejected. In addition, the present invention also provides a two-dimensional code containing product information engraved on the outer surface of the container product by ultraviolet light, so as to accurately identify and recycle the container after use.

[0029] The technical solutions of the present invention will be described in detail below in combination with specific embodiments. Example 1

[0030] Referring to the process flow of Figure 1, virgin food-grade polypropylene (about 25-30%wt of the total amount of raw materials required for molding each container) is injection molded from the A injection station of the two-component injection molding machine into the first injection cavity of the two-component mold to complete the molding of the inner layer part 104 of the container cup body in direct contact with food;

[0031] The two-component mold is rotated by 180 degrees to rotate the cup body inner layer part 104 to the second injection cavity of the mold, and the mold is closed;

[0032] The polypropylene nucleated with 10% to 30% BNT nucleation technology is mixed uniformly with 70% to 90% recycled polymer material (the mixture accounts for about 70-75%wt of the total amount of raw materials required for molding each container), and then injection molded from the B injection station of the two-component injection molding machine into the second injection cavity of the mold; physical foaming nitrogen gas is filled through the Mucell nitrogen filling device (Mucell is a registered trademark of Trexel. Co. Ltd.) during the injection station glue melting;

[0033] The mold is opened to a set stroke (usually within a distance of 5-30 mm), the outer part 105 is combined with the inner part 104 by the mold process and fixed on the back mold of the mold, air is blown to cool the mold, the outer part 105 is moved to the mold cavity shape position of the physical microcellular foaming surface required, the mold temperature is controlled to control the BNT nucleated polypropylene and nitrogen for physical microcellular foaming after the first mold opening, the outer part 105 is foamed from the initial 0.5-0.8 mm to about 2-6 times to 1.5-3.2 mm, and the combination of the inner part and the outer part is cooled and solidified.

[0034] The second mold opening is to the inner part 104 and the physical microcellular foaming outer part 105 combination (i.e. the container product) picking stroke, and the container product is ejected by the mold gas ejection system.

[0035] In the above embodiment, the wall thickness of the inner part 104 is 0.3-0.5 mm, which belongs to ultra-thin wall injection molding. This process is particularly suitable for polypropylene with a melt flow index (MFI) of 50-100 g / 10 min, and the best injection speed of the A and B injection stations is 300-500 mm / s.

[0036] In the above embodiment, in order to use the BNT nucleated microcellular gas wrapped polymeric material physical nitrogen filled microcellular foaming in a double-component double-color injection molding machine manufacturing process, a high-speed electric synchronous glue melting function needs to be configured for the injection molding equipment to support the synchronous glue melting of the injection station during mold opening and support the physical microcellular foaming process of the first mold opening.

[0037] The cross-sectional view of the container product manufactured by the process of the present embodiment is shown in FIG. 2.

[0038] After the injection molding of the container product is completed, the production and manufacturing information of the product can also be applied to the outer surface of the container for subsequent identification and tracking. The commonly used way is to use digital ultraviolet laser engraving two-dimensional code technology to integrate the product's production batch, serial number, material, color, formula, etc. information in the digital two-dimensional code on the outer surface of the container. The two-dimensional code information can be identified by using a matching special scanning device, so that when the product is recycled by using a special recycling device, the dead cycle recycling and recycling can be accurately realized according to the information of the container material, specification, model, color, etc., the efficiency of recycling and recycling is improved, and the use of raw materials is reduced and carbon emissions are reduced. Embodiment 2

[0039] In this embodiment, high density polyethylene is used instead of polypropylene in the embodiment 1, the virgin polyethylene accounts for about 28-32% wt of the raw material required for each container molding, the polyethylene mixture (containing 10%-30% BNT nucleated polyethylene and 70%-90% recycled polyethylene material) accounts for about 68-72% wt of the raw material required for each container molding, and the rest of the process is the same as that of the embodiment 1. The MFI of the high density polyethylene is preferably 50-70 g / 10 min.

[0040] The above embodiments only express several embodiments of the present application, which are described in more detail and in more detail, but cannot be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method of forming a disposable container, characterized by, The method comprises the following steps: injecting a virgin polymer material into a first injection cavity of a two-component mold from a first injection station of a two-component injection molding machine to form an inner layer of a container; rotating the two-component mold by 180 degrees to rotate the formed inner layer of the container to a second injection cavity of the two-component mold and close the mold; injecting a recycled polymer mixture into the second injection cavity of the two-component mold from a second injection station of the two-component injection molding machine to form an outer layer of the container; filling the injection station with nitrogen gas while melting the material; opening the mold once to fix the outer layer of the container and the inner layer of the container on a back mold of the mold, starting a mold blowing cooling system, moving the outer layer of the container and the back mold to a mold cavity position where a physical microcellular foaming surface is needed, controlling a mold temperature control system, and foaming the outer layer of the container to a preset wall thickness using nitrogen gas; opening the mold twice to eject the formed container product.

2. The molding method according to claim 1, characterized by, The recycled polymer mixture comprises 10% to 30% of a BNT nucleated polymer by weight, and 70% to 90% of a recycled polymer by weight.

3. The forming method according to claim 1 or 2, characterized in that, The polymer is polyethylene or polypropylene.

4. The molding method according to claim 3, characterized by The weight ratio of the virgin polymer to the recycled polymer mixture is [1:3] to [1:2].

5. The molding method according to claim 3, characterized by, The melt flow index of the polypropylene is 50 to 100.

6. The molding method according to claim 1, characterized by, The wall thickness of the inner layer of the container is 0.3 mm to 0.5 mm.

7. The molding method according to claim 1, characterized by, The initial wall thickness of the outer layer of the container is 0.5 mm to 0.8 mm, and the foamed thickness is 2 to 6 times the initial thickness.

8. The molding method according to claim 1, characterized by, The injection speed of the first injection station and the second injection station is 300 mm / s to 500 mm / s.

9. The molding method according to claim 1, characterized by, The molding temperature is 190°C to 215°C, the temperature of a front mold of the mold is 70°C to 80°C, and the temperature of a back mold of the mold is 40°C to 50°C.

10. The molding method according to claim 1, characterized by, The filling pressure of the injection molding is 80 bar to 100 bar, and the injection speed is 70% to 80%.

11. The molding method according to claim 1, characterized by, The method further comprises a step of applying product information on the outer surface of the foamed outer layer of the container.

12. The molding method according to claim 10, wherein The product information comprises the production batch, serial number, material, color, and / or formula of the product.

13. The molding method according to claim 10, wherein The product information is engraved on the outer surface of the container by digital ultraviolet laser engraving, and the product information is integrated into a two-dimensional code.

14. A disposable container prepared by the molding method of any one of claims 1 to 13.

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