CN113787666A - Method for improving appearance of injection molding product by using post-consumer recycled material - Google Patents
Method for improving appearance of injection molding product by using post-consumer recycled material Download PDFInfo
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/0001—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor characterised by the choice of material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/0005—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor using fibre reinforcements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/766—Measuring, controlling or regulating the setting or resetting of moulding conditions, e.g. before starting a cycle
Abstract
The invention provides a method for improving the appearance of an injection molding product by using a post-consumer recycled material, which comprises the following steps: respectively testing the flow processing performance parameters of the original injection molding material and the modified injection molding material, wherein the modified injection molding material is obtained by mixing the consumed recycled material with the original injection molding material in a first specified proportion; determining whether the post-consumer recycled material can be used for improving the appearance of the injection molded product at a first specified ratio according to the flow processing performance parameters of the original injection molding material and the modified injection molding material; if the situation that the post-consumer recycled material can be used for improving the appearance of the injection molding product under the first specified proportion is determined, determining injection molding process conditions corresponding to the modified injection molding material; and carrying out injection molding on the modified injection molding material according to the injection molding process conditions to obtain the injection molding product with improved appearance. The invention can effectively improve the appearance of the injection molding product without increasing the mold temperature and shorten the molding period.
Description
Technical Field
The invention relates to the technical field of injection products, in particular to a method for improving the appearance of an injection product by using a post-consumer recycled material.
Background
In the fields of consumer electronics and automobiles, consumers have higher and higher requirements for the appearance of various injection molded products, and spray-free injection molded products with bright color, high gloss and balanced mechanical strength also become targets pursued by numerous manufacturers. In order to improve the appearance of injection-molded articles, existing solutions start mainly from two aspects. In the first aspect, the appearance improvement is performed from the perspective of an injection molding process, and a relatively high mold temperature is generally adopted to increase the fluidity of a melt, but the high mold temperature tends to prolong a molding cycle, and a rapid cooling and rapid heating process needs additional equipment investment. The second aspect, which is the improvement of appearance from the raw material point of view, generally requires adjustment of the melt index and molecular weight distribution of the plastic raw material, but development of a new product brand often requires high labor and time costs. In addition, in many practical application scenarios, how to effectively balance the appearance and the physical and mechanical properties of the injection molded product also becomes a troublesome problem. For example, for applications requiring relatively high impact resistance, polycarbonate materials having relatively low melt indices are often selected, but too low a melt index often presents a number of appearance problems; for the occasions with particularly high requirements on strength and modulus, fiber adding materials are usually selected, but the addition of glass fibers often causes fiber floating on the surface of an injection molding product and seriously affects the appearance; for products with spray-free requirements, the appearance and abrasion resistance are often difficult to balance.
Therefore, there is a need to develop a new method for improving the appearance of injection molded articles.
Disclosure of Invention
In view of the above, a method for improving the appearance of injection molded articles using post-consumer recycled materials is proposed that overcomes or at least partially solves the above mentioned problems.
An object of the present invention is to provide a method for improving the appearance of an injection molded article using post-consumer recycled materials, which can shorten the molding cycle while effectively improving the appearance of the injection molded article.
It is a further object of the present invention to further enhance the effect of improving the appearance of an injection-molded article.
It is a still further object of the present invention to improve the appearance of injection molded articles while maintaining the mechanical strength of the injection molded articles.
In particular, according to an aspect of embodiments of the present invention, there is provided a method of improving the appearance of an injection molded article using post-consumer recycled material, comprising:
respectively testing the flow processing performance parameters of an original injection molding material and a modified injection molding material, wherein the modified injection molding material is obtained by mixing a post-consumer recycled material with a first specified proportion in the original injection molding material;
determining whether the post consumer recycled material is available at the first specified ratio for improving injection molded article appearance based on the flow processability parameters of the original injection molded material and the modified injection molded material;
if the situation that the post-consumer recycled material can be used for improving the appearance of an injection molding product under the first specified proportion is determined, determining injection molding process conditions corresponding to the modified injection molding material;
and carrying out injection molding on the modified injection molding material according to the injection molding process conditions to obtain an injection molding product with improved appearance.
Optionally, the flow processability parameter comprises 103-104Shear viscosity and average molecular weight at shear rate per second;
said step of determining whether said post consumer recycled material is available at said first specified ratio for improving the appearance of an injection molded article based on said flow processability parameters of said original injection molded material and said modified injection molded material comprises:
judging whether the shear viscosity of the modified injection molding material is lower than that of the original injection molding material and the average molecular weight of the modified injection molding material is lower than that of the original injection molding material;
if so, determining that the post-consumer recycled material is available at the first specified ratio to improve the appearance of the injection molded article;
if not, determining that the post consumer recycled material is not available at the first specified ratio to improve the appearance of the injection molded article.
Optionally, the step of separately testing the flow processability parameters of the original injection molding material and the modified injection molding material comprises:
testing the original and modified injection-molded materials 10 by capillary rheometer3-104Shear viscosity at shear rate per second;
the average molecular weights of the original and modified injection-molded materials were measured by gel permeation chromatography, respectively, wherein the average molecular weights include number average molecular weight and/or weight average molecular weight.
Optionally, the step of determining the injection molding process condition corresponding to the modified injection molding material includes:
and carrying out molding tests on the modified injection molding material under different process conditions by using a mold for evaluating the appearance of the injection molding product, and determining the injection molding process conditions corresponding to the modified injection molding material according to the appearance evaluation result of the product obtained by the molding tests, wherein the mold comprises a characteristic for evaluating appearance defects of the injection molding material in the filling process of a mold cavity.
Optionally, the features of the mold comprise at least one of: specifying wall thickness, a plurality of through holes with different sizes, transverse ribs, longitudinal ribs and screw columns;
the appearance defects include at least one of: short shot, weld mark, dent, shrinkage, flow mark, floating fiber.
Optionally, the molding test is a simulation molding test;
the step of performing molding tests on the modified injection molding material by using the mold under different process conditions and determining injection molding process conditions corresponding to the modified injection molding material according to appearance evaluation results of products obtained by the molding tests comprises the following steps:
acquiring a simulation mould model corresponding to the mould and data of the modified injection molding material required by the simulation forming test;
and performing mold flow analysis through specified software based on the simulation mold model and the data of the modified injection molding material, and determining injection molding process conditions corresponding to the modified injection molding material according to the filling process, the flow wave front and the appearance expression of the product of the modified injection molding material in the cavity of the mold.
Optionally, the injection molding process conditions comprise process conditions for high-speed high-temperature molding of the RHCM;
the step of injection molding the modified injection molding material according to the injection molding process conditions comprises the following steps:
and carrying out RHCM injection molding on the modified injection molding material according to the process conditions of the RHCM.
Optionally, before injection molding the modified injection molding material according to the injection molding process condition, the method further comprises:
incorporating a second specified proportion of reinforcing fibers into the modified injection molding material;
wherein the reinforcing fibers are glass fibers.
Optionally, the first specified proportion is in the range of 30% to 75%.
Optionally, after obtaining the injection molded article with improved appearance, the method further comprises:
testing the mechanical properties of the injection molded article, the mechanical properties including at least one of tensile strength, flexural modulus and impact strength.
The method for improving the appearance of the injection molding product by using the post-consumer recycled material comprises the steps of firstly evaluating whether a modified injection molding material obtained by mixing the post-consumer recycled material with the original injection molding material in a first specified proportion can be used for improving the appearance of the injection molding product, determining injection molding process conditions corresponding to the modified injection molding material after the evaluation and the determination are available, and finally performing injection molding on the modified injection molding material according to the determined injection molding process conditions to obtain the injection molding product with the improved appearance. Because the fluidity of the post-consumer recycled material is better when the material is reprocessed, the method of the invention can effectively improve the appearance of the injection molding product and shorten the molding cycle under the condition of not increasing the mold temperature by adding the screened available post-consumer recycled material into the original injection molding material (or called original raw material). In addition, the characteristics of small average molecular weight of the recycled material after consumption are utilized, and the flowability and the processability of the injection molding material are adjusted by blending the recycled material with the virgin material, so that the time and the labor cost for developing new marks and new products can be effectively saved. In addition, the invention applies the post-consumer recycled material to the manufacture of injection molding products (particularly appearance parts), develops a new direction of the application of the post-consumer recycled material, and effectively improves the value of resource recycling.
Furthermore, the invention can further enhance the effect of improving the appearance of the injection molding product by combining the high-speed high-temperature molding RHCM process on the basis of blending the post-consumer recycled material in the primary material.
Further, the present invention can maintain the mechanical strength of the injection molded article while improving the appearance of the injection molded article by further adding a reinforcing fiber (e.g., glass fiber) to the modified injection molded material blended with the post-consumer recycled material.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 shows a schematic flow diagram of a method for improving the appearance of an injection molded article using post consumer recycled material according to an embodiment of the present invention;
FIG. 2 shows a schematic flow diagram of a method for improving the appearance of an injection molded article using post consumer recycled material according to another embodiment of the present invention;
FIG. 3 shows a schematic structural view of a mold for evaluating the appearance of an injection molded article according to an embodiment of the present invention;
FIG. 4 is a graph comparing shear viscosity and molecular weight data measured for PC/ABS virgin stock and PC/ABS modifier containing 35% PCR in example 1 of the present invention;
FIG. 5 is a comparative graph showing the appearance of PC/ABS raw stock and PC/ABS modified material containing 35% PCR obtained by mold flow analysis in example 1 of the present invention;
FIG. 6 is a comparative graph showing the appearance of an actual injection-molded article of PC/ABS virgin stock and PC/ABS modified stock containing 35% PCR in example 1 of the present invention;
FIG. 7 is a comparative graph showing the appearance of an actual injection-molded article of PC virgin stock, PC modifier containing 30% PCR, PC virgin stock to which 30% GF has been added, and PC modifier containing 30% PCR to which 30% GF has been added in example 2 of the present invention;
FIG. 8 is a comparative graph showing the appearance of the actual injection molded articles of PC/ABS virgin stock and PC/ABS modified stock containing 75% PCR in example 3 of the present invention at a mold temperature of 95 ℃ and a mold temperature of 125 ℃ for the RHCM process.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In recent years, development of circular economy has become a topic of intense interest to various industries. Post-Consumer Recycled materials (PCR) generally refer to waste plastic materials produced after circulation, consumption and use. How to evaluate and use the PCR material and find a suitable application scene of the PCR material is an important step for realizing green development of the industry.
The inventors of the present application found that the melt index of the injection molding material is an important factor affecting the appearance of the article in view of the molecular structure of the material. After a period of time, the plastic material may be degraded and aged, so that the average molecular weight may be reduced, thereby improving the fluidity of the PCR material during reprocessing. The inventors consider that the PCR material is used to adjust the melt index of the injection molding material, and thus it is possible to improve the appearance of the injection molded article, but at the same time the mechanical strength of the article may be affected. Therefore, the reasonable and effective evaluation of the structural and performance changes of the PCR material is the key to the application of the PCR material to injection molded articles.
In order to solve or at least partially solve the technical problems of the existing scheme for improving the appearance of the injection-molded product, the embodiment of the invention provides a method for improving the appearance of the injection-molded product by using a post-consumer recycled material, and the appearance of the injection-molded product is effectively improved without increasing the molding cycle by evaluating the molecular structure of a PCR material and determining the injection-molding process conditions of the PCR modified injection-molded material.
FIG. 1 shows a schematic flow diagram of a method for improving the appearance of an injection molded article using post-consumer recycled material according to an embodiment of the present invention. Referring to fig. 1, the method may include at least the following steps S100 to S400.
And S100, respectively testing the flow processing performance parameters of the original injection molding material and the modified injection molding material, wherein the modified injection molding material is obtained by mixing the consumed recycled material with the original injection molding material in a first specified proportion.
And S200, determining whether the post-consumer recycled material can be used for improving the appearance of the injection molding product at a first specified ratio according to the flow processing performance parameters of the original injection molding material and the modified injection molding material. If so, i.e., if it is determined that the post-consumer recycled material is available at the first specified ratio for improving the appearance of the injection molded article, step S300 is performed. If not, the process is ended.
And S300, determining injection molding process conditions corresponding to the modified injection molding material.
And S400, performing injection molding on the modified injection molding material according to injection molding process conditions to obtain an injection molding product with improved appearance.
The method for improving the appearance of the injection molding product by using the post-consumer recycled material comprises the steps of firstly evaluating whether a modified injection molding material (or called modified material) obtained by mixing the post-consumer recycled material with a first specified proportion in an original injection molding material (or called original raw material) can be used for improving the appearance of the injection molding product, determining injection molding process conditions corresponding to the modified injection molding material after the evaluation and the determination of the availability, and finally performing injection molding on the modified injection molding material according to the determined injection molding process conditions to obtain the injection molding product with improved appearance. Because the fluidity of the post-consumer recycled material is better when the material is reprocessed, the method of the invention can effectively improve the appearance of the injection molding product and shorten the molding cycle under the condition of not increasing the mold temperature by adding the screened available post-consumer recycled material into the original injection molding material. In addition, the characteristics of small average molecular weight of the recycled material after consumption are utilized, and the flowability and the processability of the injection molding material are adjusted by blending the recycled material with the virgin material, so that the time and the labor cost for developing new marks and new products can be effectively saved. In addition, the invention applies the post-consumer recycled material to the manufacture of injection molding products (particularly appearance parts), develops a new direction of the application of the post-consumer recycled material, and effectively improves the value of resource recycling. The method of the invention is more suitable for the application of the appearance piece, because the addition of PCR in the injection molding material can reduce the mechanical strength of the injection molding product.
The virgin injection molding material may be a common plastic material, including but not limited to PC (Polycarbonate), PC/ABS (Acrylonitrile-Butadiene-Styrene Copolymer), and the like. It will be appreciated by those skilled in the art that in the method of the invention, the PCR material and the original casting material used for it may generally be the same type or similar plastic material. For example, when the original casting material is PC, the PCR material used is that of PC. When the original injection molding material is PC/ABS, the PCR material used is also the PCR material of PC. Of course, in some cases, the PCR material and the original injection molding material can be different kinds of plastic materials, which does not affect the solution of the present invention.
In embodiments of the present invention, the flow processability parameter can be any parameter that characterizes the flowability and processability of the injection molding material.
In one embodiment, the flow processability parameter can include a high shear rate (e.g., a shear rate of 10)3-104Shear viscosity and average molecular weight per second). More specifically, the average molecular weight may include a number average molecular weight and/or a weight average molecular weight.
Accordingly, referring to fig. 2, in one embodiment, step S200 may be further implemented as step S201: and judging whether the shear viscosity of the modified injection molding material is lower than that of the original injection molding material and the average molecular weight of the modified injection molding material is lower than that of the original injection molding material. If, i.e. if the shear viscosity of the modified injection-molding material is lower than the shear viscosity of the original injection-molding material and the average molecular weight of the modified injection-molding material is lower than the average molecular weight of the original injection-molding material, it is determined that the post-consumer recycled material is useful for improving the appearance of the injection-molded article at the first specified ratio. If not, namely if the shear viscosity of the modified injection molding material is not lower than the shear viscosity of the original injection molding material or the average molecular weight of the modified injection molding material is not lower than the average molecular weight of the original injection molding material, determining that the recycled material after consumption cannot be used for improving the appearance of the injection molding product under the first specified proportion, and ending the process.
The higher zero-shear viscosity and more pronounced shear thinning behavior of the modified injection molding material generally results in a lower shear viscosity at high shear rates than the original injection molding material; meanwhile, the modified injection molding material has a lower average molecular weight, which indicates that the addition of PCR can adjust the molecular structure of the original injection molding material. When the above two conditions are satisfied simultaneously, it is shown that the modified injection molding material containing PCR has better fluidity at a high shear rate than the virgin material, and therefore, the PCR can be attempted for improving the appearance of injection molded articles.
In the embodiment of the invention, the molecular structure and performance of the raw material and the modified material are evaluated according to the flow processing performance parameters (specifically, the shear viscosity and the average molecular weight under high shear rate) of the raw material and the modified material, so that the applicable PCR material can be screened out conveniently and accurately.
In one embodiment, referring to fig. 2, step S100 may be further implemented as:
step S101, respectively testing the high shear rates (such as 10) of the original injection molding material and the modified injection molding material by a capillary rheometer3-104Shear viscosity per second shear rate);
and S102, respectively testing the average molecular weights of the original injection molding material and the modified injection molding material through gel permeation chromatography.
The capillary rheometer is a device for measuring shear stress rate under high stress, can draw a shear viscosity-shear rate relation curve and a plasticizing curve of a thermoplastic material, measure the viscosity, viscous flow activation property and the like of a high polymer melt, and is very suitable for measuring the shear viscosity of an injection molding material under high shear rate. Gel Permeation Chromatography (GPC), also called size exclusion Chromatography, is mainly used for the relative molecular mass fractionation analysis and relative molecular mass distribution test of high polymers. The order of step S101 and step S102 may be interchanged or performed simultaneously.
The steps of testing the shear viscosity and the average molecular weight of the original injection molding material and the modified injection molding material and the step of evaluating and screening the PCR material are combined into a simple and feasible method for evaluating the application feasibility of the PCR material. The evaluation method utilizes a gel permeation chromatograph and a capillary rheometer to carry out initial evaluation on the molecular structures and rheological characteristics of the original raw material and the modified material containing the PCR, analyzes the differences of the structures and the performances of the original raw material and the modified material, and carries out primary screening on the PCR material. The PCR material screened by the evaluation method can effectively improve the appearance of the injection molding product and shorten the molding period under the condition of not increasing the mold temperature.
In some cases, the molecular weight distributions of the original and modified injection-molded materials can also be measured by GPC. The broader molecular weight distribution and lower average molecular weight of the modified injection molding material may indicate better flowability thereof.
In one embodiment, referring to fig. 2, step S300 may be further implemented as step S301: and carrying out molding tests on the modified injection molding material under different process conditions by using a mold for evaluating the appearance of the injection molding product, and determining the injection molding process conditions corresponding to the modified injection molding material according to the appearance evaluation result of the product obtained by the molding tests. The mold used in this step is a mold specifically designed and manufactured for evaluating the appearance of an injection-molded article of an injection-molded material (virgin stock and/or a modified material containing PCR), and includes a feature for evaluating appearance defects occurring during filling of a cavity of the mold with the injection-molded material.
Fig. 3 shows a schematic structural view of a mold 10 for evaluating the appearance of an injection-molded article according to an embodiment of the present invention. As shown in fig. 3, there may be one, two or more dies 10, and in the case of two or more dies 10, the wall thickness specifications differ between the dies 10. Two or more molds 10 may be connected with the same injection device to inject the injection molding material therethrough. The above-described features of each die 10 may include at least one of a specified wall thickness, a plurality of through-holes 1 of different sizes, transverse ribs 2, longitudinal ribs 3, studs 4, and the like. These features can be achieved through via design, rib design, reduced glue design, etc. Accordingly, the appearance defect to be evaluated of the injection molded article may include at least one of shot, weld mark, dent, shrinkage, flow mark, floating fiber, and the like.
Specifically, the specified wall thickness is preferably a thin wall thickness, such as 2mm, 1.2mm, or the like. The thin-wall design can be used for evaluating appearance defects such as short shot and the like which can occur in the process of filling injection molding materials (particularly modified materials containing PCR) in a mold cavity. The design of the through-holes 1 of different sizes can be used to evaluate the possible weld marks of injection-molded articles of injection-molded material, in particular of PCR-containing modifications. The design of the transverse ribs 2 and the longitudinal ribs 3 can be used to evaluate the possible occurrence of dents on the back of the injection-molded article. The design of the screw boss 4 can be used to evaluate the indentation of the back surface of the injection molded article and the pull force test of the injection molded article. It should be noted that the size and layout of the features of the mold 10 in fig. 3 are only schematic, and other sizes and layouts may be designed according to actual requirements in practical applications.
In an embodiment, the molding test performed in step S301 may be a simulation molding test, and step S301 may be further embodied as: acquiring a simulation mould model corresponding to the mould 10 and data of a modified injection molding material required by a simulation forming test; and based on the data of the simulation mould model and the modified injection molding material, carrying out mould flow analysis through specified software, and determining the injection molding process condition corresponding to the modified injection molding material according to the filling process, the flow wave front and the appearance expression of the product of the modified injection molding material in the cavity of the mould. More specifically, in the simulation molding test, the process conditions are adjusted according to the filling integrity, the molding speed, whether the product shrinks or warps, and the like, and finally the injection molding process conditions which meet the requirements and are even optimal are determined.
In a particular embodiment, a simulated mold model may be generated by inputting various parameters of the mold 10 into a simulation tool. The specific software for performing modular flow analysis may be Moldex3D, although any other suitable modular flow analysis software may be used.
In the embodiment, the injection molding process conditions are determined through mold flow analysis, so that the efficiency can be greatly improved, and the consumption of materials and manpower is reduced.
In addition, when the mold flow analysis is carried out, the original injection molding material can be simultaneously and correspondingly analyzed, and the analysis results of the original injection molding material and the modified injection molding material are compared, so that the improvement effect is more intuitively analyzed.
In another embodiment, the molding test performed in step S301 may also be an actual physical molding test. In a physical molding test, the process conditions can be adjusted according to the filling integrity, the molding speed, whether the product shrinks or warps and the like, and finally the injection molding process conditions which meet the requirements and are even optimal are determined.
The determined injection molding process conditions may include injection molding temperature, injection molding pressure, dwell time, mold temperature, and the like. And guiding the actual injection molding process by using the determined injection molding process conditions to ensure the appearance improvement effect of the injection molded product.
In a preferred embodiment, the injection Molding process condition may include a process condition of Rapid Heat Cycle Molding (RHCM), and when determining the injection Molding process condition corresponding to the modified injection Molding material, the RHCM process condition corresponding to the modified injection Molding material may also be determined. Accordingly, the modified injection molding material may be subjected to RHCM injection molding according to the determined RHCM process condition in step S400.
In the embodiment, the improvement effect of the appearance of the injection molding product can be further enhanced by combining the RHCM process on the basis of blending the PCR material in the primary material. The method of the embodiment is particularly suitable for manufacturing injection molded products with higher requirements on appearance and higher value.
As mentioned above, the addition of PCR materials may affect the mechanical strength of the product. Thus, in some embodiments, a second specified proportion of reinforcing fibers may also be incorporated into the modified injection-molded material prior to injection molding the modified injection-molded material according to the determined injection-molding process conditions to enhance the mechanical properties of the resulting injection-molded article. The reinforcing fibers may be any reinforcing fibers commonly used in plastic materials, and preferably may be Glass Fibers (GF).
In this embodiment, by further adding a reinforcing fiber (e.g., glass fiber) to the modified injection molding material blended with the PCR material, the mechanical strength of the injection molded article can be maintained while the appearance of the injection molded article is improved. The method of the present embodiment is particularly suitable for the manufacture of injection molded articles (e.g., structural members) having high requirements for appearance and mechanical properties.
Numerous experiments have shown that the first specified proportion can be any value in the range of 30% to 75%, such as 30%, 35%, 50%, 60%, 75%, etc. The second specified proportion may be any value in the range of 10% to 30%, such as 10%, 15%, 20%, 30%, etc. In these proportions, a good appearance-improving effect and a good mechanical property-maintaining effect of the injection-molded article can be achieved.
In one embodiment, referring to fig. 2, after step S400, the method may further include step S500: the mechanical properties of the injection molded articles were tested. Specifically, the mechanical properties may include at least one of tensile strength, flexural modulus, impact strength, and the like. And finally, whether the injection molding product with the improved appearance meets the mechanical property requirement is inspected through testing the mechanical property of the injection molding product.
While various embodiments of the aspects of the method for improving the appearance of an injection molded product using post-consumer recycled materials according to the present invention have been described above, the following embodiments of the method for improving the appearance of an injection molded product using post-consumer recycled materials according to the present invention are described with reference to specific examples, and other advantages and effects of the present invention will be apparent to those skilled in the art from the disclosure in the specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Example 1
In the embodiment, 35% of PCR is added to improve the dent defect of the appearance of the PC/ABS injection molding product, and the specific method comprises the following steps:
(1) the molecular structure and performance of the PC/ABS raw material and the PC/ABS modified material containing 35% of PCR PC are tested and evaluated by using a capillary rheometer and a gel permeation chromatograph, and the modified material containing 35% of PCR is found to have higher zero-cut viscosity and more obvious shear thinning behavior. Meanwhile, GPC results show that the PCR-containing modifier has a broader molecular weight distribution and a lower average molecular weight. And (4) preliminary evaluation results: PC/ABS modification by 35% PCR at high shear rate (10)3-104In the/sec range) has better flowability than virgin material and can be used in preliminary attempts to improve the appearance of injection-molded articles. The shear viscosity and molecular weight data for the virgin and modified stocks are shown in FIG. 4.
(2) Using the mold 10 design of fig. 3, Moldex3D mold flow simulation analysis was performed to determine the injection molding process conditions for the 35% PCR PC/ABS modification. Meanwhile, in the simulation analysis of the mold flow, the simulated appearance of the injection molding product of the modified material can be obtained.
(3) And (3) performing injection molding on the PC/ABS modified material with 35% of PCR by adopting the injection molding process conditions determined in the step (2) to obtain an actual injection molded product.
(4) And carrying out mechanical property test and evaluation on the obtained actual injection molding product to obtain mechanical property data. Specifically, the actual injection molded article was subjected to tensile strength and notched izod impact strength tests.
Meanwhile, in the embodiment, the PC/ABS virgin material is used as a comparative example, and is subjected to the steps (2) to (4) under the same condition as the PC/ABS modified material of 35% PCR, so that the simulated appearance of the injection molded product of the virgin material, the actual injection molded product and the mechanical property data of the actual injection molded product are obtained, and the simulated appearance, the actual injection molded product and the mechanical property data of the actual injection molded product are compared with the result of the modified material.
FIG. 5 is a graph showing a comparison of the appearance of PC/ABS virgin material and PC/ABS modified material containing 35% PCR obtained by mold flow analysis in this example, wherein (a) is a schematic view of the appearance of the virgin material at normal mold temperature, (b) is a schematic view of the appearance of the modified material at normal mold temperature, (c) is a schematic view of the appearance of the virgin material at RHCM, and (d) is a schematic view of the appearance of the modified material at RHCM. It will be understood by those skilled in the art that the normal mold temperature is relative to the mold temperature at RHCM. As can be seen from the comparison of (a) and (b) and the comparison of (c) and (d), the molded article of the modified material had a shallower dent in appearance than the virgin material, corresponding to the screw post 4, the transverse ribs 2 and the longitudinal ribs 3, at the normal mold temperature and the RHCM. In addition, as can be seen from the comparison of (b) and (d), the indentations corresponding to the studs 4, the transverse ribs 2 and the longitudinal ribs 3 were shallower in the appearance of the injection-molded article of the modified material under RHCM than the indentations corresponding to the normal molding temperature. This shows that the mold flow simulation analysis results show that the addition of 35% PCR can effectively improve the appearance dent defect of the injection molded product.
FIG. 6 is a graph showing the comparison of the appearance of the PC/ABS green stock and the PC/ABS modified stock containing 35% PCR in this example, wherein (a) is a schematic view of the appearance of the actual injection-molded article of the green stock at normal mold temperature, and (b) is a schematic view of the appearance of the actual injection-molded article of the modified stock at normal mold temperature. As can be seen by comparing (a) and (b) in FIG. 6, the appearance of the actual injection molded article is well matched with the result of the mold flow simulation analysis, and it is further proved that the addition of 35% PCR to PC/ABS can effectively improve the appearance indentation of the injection molded article.
Due to the addition of 35% PCR, the mechanical properties of the material may be negatively affected. After tensile strength and cantilever beam notch impact strength tests, the breaking tensile strength of the modified material and the breaking tensile strength of the primary material are respectively 48.4MPa and 56.3MPa, and the impact strength is respectively 47.2kJ/m2And 51.5kJ/m2The modified material added with the PCR material is weaker in mechanical strength, and needs to be careful when being used in structural parts with higher requirements on mechanical properties.
Example 2
In the embodiment, 35% of PCR and 30% of glass fiber are added into PC to improve the surface floating of the injection molding product, and simultaneously, the good mechanical strength of the injection molding product is kept. The specific method comprises the following steps:
actual injection-molded articles of the above four raw materials at normal mold temperature and RHCM were obtained by sequentially performing steps (1) to (4) of example 1 using PC raw material, PC-modified material containing 30% of PCR, PC raw material containing 30% of glass fiber, and PC-modified material containing 30% of PCR and 30% of glass fiber as raw materials, and their external appearances are shown in FIG. 7, for example.
FIG. 7 is a comparison graph showing the appearance of actual injection-molded articles of PC virgin stock, PC modifier containing 30% PCR, PC virgin stock added with 30% GF, and PC modifier containing 30% PCR added with 30% GF according to the present invention, wherein (a), (b), (c), (d) are respectively schematic appearances of actual injection-molded articles of the above four raw materials at normal mold temperature, and (e), (f), (g), and (h) are respectively schematic appearances of actual injection-molded articles of the above four raw materials under RHCM. It should be noted that in (a), obvious dent defects corresponding to the studs 4 and the transverse ribs 2 are respectively circled by ellipses.
Comparative analysis shows that the PC modified material containing 30% PCR has better appearance than the PC raw material, and the indentation is obviously weakened. After 30% of glass fiber is added into the PC raw material, the surface of the injection molding product has obvious fiber floating phenomenon, and the surface fiber floating phenomenon of the injection molding product can be obviously improved by adding 30% of PCR or adopting RHCM high mold temperature condition (specifically 170 ℃). Therefore, compared with the RHCM high-mold-temperature process, the surface floating fiber is improved by adding the PCR material, the forming period can be effectively shortened, the investment of RHCM equipment is avoided, and the cost is reduced.
The mechanical property evaluation result shows that the mechanical property difference between the original raw material and the modified material added with the PCR can be obviously reduced by adding the PCR material and the glass fiber at the same time. Specifically, the breaking tensile strength of the PC raw material (namely PC + 30% GF) added with 30% GF and the breaking tensile strength of the PC modified material (namely 30% PCR PC + 30% GF) containing 30% PCR and added with 30% GF are 113MPa and 127MPa respectively, the bending modulus is 7170MPa and 8120MPa respectively, and the notched izod impact strength is 17.9kJ/m2And 16.1kJ/m2. It can be found that PCR and glass fiber produce synergistic effect, so that the mechanical strength of the injection molding product of the modified material is almost not different from that of the original material, and the modified material can be applied to structural members.
Example 3
In this example, 75% PCR was added to PC/ABS to improve surface sink marks on injection molded articles.
The procedure of this example is the same as in example 2, except that the raw PC/ABS material and the 75% PCR-containing PC/ABS modifier are used as the raw materials. The appearance of the resulting actual injection-molded article is shown in FIG. 8.
FIG. 8 shows a comparison of the appearance of the PC/ABS virgin material and the PC/ABS modified material containing 75% PCR of the present example at 95 ℃ mold temperature and 125 ℃ mold temperature of the RHCM process. Comparative analysis found that the addition of 75% PCR was effective in improving surface sink marks of injection molded articles. And the high-gloss appearance of the injection molding product can be realized by adding the PCR material and combining the RHCM quenching and rapid heating technology.
In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (10)
1. A method of improving the appearance of an injection molded article using post consumer recycled material, comprising:
respectively testing the flow processing performance parameters of an original injection molding material and a modified injection molding material, wherein the modified injection molding material is obtained by mixing a post-consumer recycled material with a first specified proportion in the original injection molding material;
determining whether the post consumer recycled material is available at the first specified ratio for improving injection molded article appearance based on the flow processability parameters of the original injection molded material and the modified injection molded material;
if the situation that the post-consumer recycled material can be used for improving the appearance of an injection molding product under the first specified proportion is determined, determining injection molding process conditions corresponding to the modified injection molding material;
and carrying out injection molding on the modified injection molding material according to the injection molding process conditions to obtain an injection molding product with improved appearance.
2. The method of claim 1, wherein the flow processability parameter comprises 103-104Shear viscosity and average molecular weight at shear rate per second;
said step of determining whether said post consumer recycled material is available at said first specified ratio for improving the appearance of an injection molded article based on said flow processability parameters of said original injection molded material and said modified injection molded material comprises:
judging whether the shear viscosity of the modified injection molding material is lower than that of the original injection molding material and the average molecular weight of the modified injection molding material is lower than that of the original injection molding material;
if so, determining that the post-consumer recycled material is available at the first specified ratio to improve the appearance of the injection molded article;
if not, determining that the post consumer recycled material is not available at the first specified ratio to improve the appearance of the injection molded article.
3. The method of claim 2, wherein the step of separately testing the flow processability parameters of the original injection molded material and the modified injection molded material comprises:
testing the original and modified injection-molded materials 10 by capillary rheometer3-104Shear viscosity at shear rate per second;
the average molecular weights of the original and modified injection-molded materials were measured by gel permeation chromatography, respectively, wherein the average molecular weights include number average molecular weight and/or weight average molecular weight.
4. The method of claim 1, wherein the step of determining injection molding process conditions for the modified injection molding material comprises:
and carrying out molding tests on the modified injection molding material under different process conditions by using a mold for evaluating the appearance of the injection molding product, and determining the injection molding process conditions corresponding to the modified injection molding material according to the appearance evaluation result of the product obtained by the molding tests, wherein the mold comprises a characteristic for evaluating appearance defects of the injection molding material in the filling process of a mold cavity.
5. The method of claim 4, wherein the features of the mold comprise at least one of: specifying wall thickness, a plurality of through holes with different sizes, transverse ribs, longitudinal ribs and screw columns;
the appearance defects include at least one of: short shot, weld mark, dent, shrinkage, flow mark, floating fiber.
6. The method of claim 4, wherein the forming test is a simulated forming test;
the step of performing molding tests on the modified injection molding material by using the mold under different process conditions and determining injection molding process conditions corresponding to the modified injection molding material according to appearance evaluation results of products obtained by the molding tests comprises the following steps:
acquiring a simulation mould model corresponding to the mould and data of the modified injection molding material required by the simulation forming test;
and performing mold flow analysis through specified software based on the simulation mold model and the data of the modified injection molding material, and determining injection molding process conditions corresponding to the modified injection molding material according to the filling process, the flow wave front and the appearance expression of the product of the modified injection molding material in the cavity of the mold.
7. The method of claim 1, wherein the injection molding process conditions include process conditions for high speed high temperature molding of the RHCM;
the step of injection molding the modified injection molding material according to the injection molding process conditions comprises the following steps:
and carrying out RHCM injection molding on the modified injection molding material according to the process conditions of the RHCM.
8. The method of claim 1, wherein prior to injection molding the modified injection molded material according to the injection molding process conditions, the method further comprises:
incorporating a second specified proportion of reinforcing fibers into the modified injection molding material;
wherein the reinforcing fibers are glass fibers.
9. The method of claim 1, wherein the first specified proportion is in the range of 30% to 75%.
10. The method of claim 1, wherein after obtaining the appearance-improved injection molded article, the method further comprises:
testing the mechanical properties of the injection molded article, the mechanical properties including at least one of tensile strength, flexural modulus and impact strength.
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