JP2002241603A - Polyamide-based resin composition molded article and method for injection-molding the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the production of a polyamide-based resin composition molded article by facilitating the charging of a melted polyamide-based resin into a cavity of a mold without limiting the mol.wt. of the polyamide-based resin and enhancing the temperature of the resin up to a higher temperature than a needed temperature when injection-molded. SOLUTION: This polyamide-based resin composition molded article is characterized by being obtained by mixing carbon dioxide pressurized to >=1 MPa with a melted polyamide-based resin composition comprising at least (A) a polyamide-based resin and at least (B) a fibrous inorganic and/or organic filler, and then charging the mixture into the cavity of a mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article made of a polyamide (hereinafter abbreviated as "PA") resin and an injection molding method thereof.

[0002]

2. Description of the Related Art Conventionally, injection molded articles made of a crystalline resin such as a PA resin have a large molding shrinkage, a large volume shrinkage due to crystallization, a low viscosity at the time of melting, as compared with an amorphous resin. It has features such as an extreme change in fluidity at the boundary of the melting point, and the volume of the molded product gradually decreases with the progress of crystallization after molding. For this reason, there are many restrictions on product design, mold design, and molding conditions, and it is difficult to maintain dimensional accuracy at a high level.

In general, when a molded product or a thin-walled molded product required at a high level of dimensional accuracy is obtained by an injection molding method of a crystalline resin, a crystalline resin having a small molecular weight is often used. This is because crystalline resin with low molecular weight is
Low viscosity and high fluidity. For this reason, the pressure is easily transmitted to the flow end of the mold cavity, and the thin portion of the product is easily filled. However, in general, a crystalline resin having a small molecular weight has higher rigidity than a crystalline resin having a large molecular weight, but has a reduced toughness and impact resistance, and has a fatigue fracture due to a repeated load, a continuous static load, and the like. , The service life tends to be short.

[0004] For this reason, it has been difficult to obtain a crystalline resin molded product having excellent toughness, impact resistance and fatigue properties in molded products and thin-walled molded products required at a high level of dimensional accuracy. On the other hand, as a method of obtaining a molded product having high dimensional accuracy by devising a mold design, it is conceivable to increase the number of gate points. By shortening the flow distance to the flow end, it is possible to easily fill the mold cavity and to apply a pressure to the entire filled resin.

[0005] However, increasing the number of gates causes an increase in the number of steps in manufacturing a mold, and also complicates the mold structure. In addition, this means increasing the volume of the sprue and runner portions. As a result, the number of parts that do not become products is increased in each molding cycle, which is not preferable in consideration of efficiency during manufacturing. In addition, by increasing the resin temperature or the mold temperature during injection molding, the speed at which the viscosity of the resin rises in the mold cavity is reduced, so that the mold can be easily filled into the mold cavity. It is also common to create a state in which pressure is easily applied to the entire resin, but a method of increasing the resin temperature causes decomposition of the resin, and a method of increasing the mold temperature causes a problem that the molding cycle becomes longer.

On the other hand, in the injection molding of a crystalline resin, as a method for securing dimensional stability after molding, a mold temperature is increased to increase the amount of shrinkage immediately after molding and to reduce the amount of dimensional change thereafter. A method of taking a long cooling time, taking out after sufficiently shrinking in a mold, and performing an annealing treatment after molding to promote crystallization in a short time to shrink the volume is adopted. . The method of increasing the mold temperature and increasing the cooling time causes problems such as a longer molding cycle, and the annealing process is a post-processing after molding, which increases the number of molding steps and causes the annealing process itself to vary. If this occurs, there is a concern that it may cause variations in the dimensions of the molded product.

On the other hand, in the conventional injection molding method, the injection pressure and the filling pressure change in proportion to the melt viscosity of the resin used. A resin having a high melt viscosity requires a high injection pressure at the time of resin injection, which results in a large amount of distortion remaining in a molded product. The molding distortion remaining in the molded article is also called “residual distortion”. This residual strain is gradually relaxed after molding, but this is often due to deformation and shrinkage of the molded product.
This is also seen when the mold structure, molding conditions, etc., are not appropriate.

The pressure applied to the resin filled in the mold cavity is preferably uniform, but the pressure distribution may be uneven near the gate and at the end of the flow. This means that it is difficult to transmit a sufficient pressure to the end portion of the flow, which causes poor appearance of the end portion of the flow, generation of voids, sink marks, expansion of molding shrinkage and unevenness. Therefore, it can be said that when filling the resin cavity into the mold cavity, it is preferable that an appropriate pressure that hardly causes residual strain to remain is transmitted uniformly to the entire cavity.

As an injection molding method for improving the dimensional accuracy with less distortion of the molded article, it is conceivable to increase the resin temperature during injection molding to lower the melt viscosity of the resin. Usually, the setting range of the resin temperature when molding the crystalline resin is narrower than that of the crystalline resin. Usually 5 to 3 from melting point
It is carried out in the range 0 ° C. higher, often in the range 10-20 ° C. above the melting point. This can be said to be a temperature range in which the viscosity of the resin is high up to a temperature range higher by about 5 ° C. than the melting point, so that the filling is difficult and the melting of the resin is not sufficient, and the melted portion and the unmelted portion are easily mixed. When the unmelted portion is mixed in the molded product, there is a concern that a problem such as a decrease in strength may occur.

On the other hand, the resin temperature during molding is 30 ° C. below the melting point.
In the above high temperature range, the decomposition of resin is promoted, and the appearance of the molded product surface is called silver (or “silver streak”),
Discoloration of the molded product itself may occur, and the generated decomposition gas may easily cause stains on the mold. This is not preferable because it may cause deterioration of the resin, may deteriorate the working environment, and may cause the mold to be disassembled and cleaned. Therefore, it can be said that there is a limit to the method of increasing the resin temperature in order to improve the fluidity of a crystalline resin having a high viscosity.

[0011] In addition, when the resin temperature is set high, the volume change of the resin itself during cooling and solidification becomes large, which is likely to cause sink marks, voids, etc., and it takes time to cool the resin. However, there is a concern that productivity may decrease. On the other hand, by increasing the mold temperature, a decrease in resin temperature and an increase in viscosity in the mold cavity can be suppressed. However, when the mold temperature is increased,
Since water cannot be used as a medium for controlling the temperature of the mold, water vapor or oil is often used, which makes the handling complicated and increases the cooling time of the resin filled in the mold. In addition, the molding cycle time is prolonged, and the size of the molded product at the time of removal is easily reduced.

In addition, in the case of injection molding in which the temperature of the mold is increased, if the cooling time is not sufficient and the cooling of the resin is insufficient, the temperature of the molded product at the time of removal is high. For this reason, after the molded article is taken out from the mold, there is a possibility that volume shrinkage or deformation due to its own weight may occur before the temperature of the molded article itself gradually decreases to the ambient temperature. This causes the dimensional accuracy to deteriorate, which is not preferable. Japanese Patent Application Laid-Open No. Sho 62-58287 discloses an injection molding method in which the surface temperature of the mold is extremely increased only when the resin is filled into the mold cavity.
No. "Injection molding method of rubber reinforced polystyrene resin",
Each is disclosed in JP-A-62-58288, "ABS resin injection molding method". Injection molding to obtain a crystalline resin molded product that has a smooth surface and good mold transferability by inserting an inductor between the molds and heating the mold surface with both molds open. Is the law.

In these injection molding methods, a step of inserting an inductor or a high-frequency induction heating coil between the molds during a molding cycle, heating the mold surface, and pulling out the inductor or the high-frequency induction heating coil from between the molds. is necessary. When this injection molding method is applied to a polyamide resin, the mold temperature is equal to or higher than the heat deformation temperature (approximately 70 ° C. for a polyamide 6-6 resin) under a load of 1.82 MPa, and preferably equal to or higher than the melting point (for a polyamide 6-6 resin). About 255-26
5 ° C).

In addition, since the molding cycle is extended due to the step of heating the mold surface, there is a problem in productivity, and in the case of high-frequency induction heating, the amount of electricity consumed is excessive, which is not preferable from the viewpoint of energy saving. . In addition, after heating the mold surface, the mold temperature gradually decreases to the temperature before heating, but it is difficult to predict the temperature decrease rate at this time, so the flow prediction of the filled resin is performed. Becomes difficult. The fact that the molded product is limited to a relatively flat molded product is also undesirable because it limits the degree of freedom in the product design of the molded product.

On the other hand, new molding methods such as a high-speed injection molding method and a gas assist molding method have been proposed as injection molding methods for crystalline resins with improved dimensional accuracy and dimensional stability. The high-speed injection molding method has the effect of injecting the crystalline resin at a high speed to prevent the melt viscosity from rising due to cooling from the mold, reduce the melt viscosity with high shearing force, and reduce the pressure difference in the cavity. is there. Further, the effect of reducing the injection time is obtained, and the productivity is also improved. However, it is necessary to pay attention to the deterioration of the resin due to the heat generated by shearing, the generation of burrs due to high-speed injection, and the occurrence of resin burn due to adiabatic compression in the gas reservoir at the end of the mold cavity.

The gas assist molding method generally forms a hollow portion in a molded product by injecting a compressed gas into a resin. The compressed gas has a pressure-holding effect from the inside of the molded article, and has the effect of suppressing the occurrence of sink marks on the molded article. The pressure-holding effect of the compressed gas is lower than the pressure-holding effect in the usual injection molding method, and the pressure-holding effect can be expected up to the end of the flow. For this reason, the residual distortion is small, the deformation of the molded product such as warpage can be reduced, and the dimensional accuracy can be expected to be improved. However, depending on the shape of the molded product, there are cases where the installation location of the gas injection port is limited, and the effect may not be sufficiently exhibited.

On the other hand, J.I. Appl. Polym. Sc
i. , Vol. 30, 2633 (1985), it is known that when carbon dioxide is absorbed into a resin, it acts as a plasticizer for the resin and lowers the glass transition temperature. It has not been widely applied to processing. Japanese Unexamined Patent Publication No. Hei 5-318541 discloses a method in which a gas such as carbon dioxide or nitrogen is contained in a thermoplastic resin, and the resin is filled in the cavity while removing the gas in the cavity. To obtain a molded article without deterioration in strength and appearance. However, in this method, when carbon dioxide is used as the gas, the amount of the gas contained in the resin is small at a maximum of about 0.18% by weight, and it can be said that it is difficult to obtain a sufficient effect of improving the fluidity.

Further, WO 98/52734 discloses that
In injection molding of thermoplastic resin,
Shows a method of filling molten resin whose viscosity has been reduced by dissolving more than 1% by weight into a mold cavity that has been kept pressurized with a gas such as carbon dioxide at a pressure higher than the pressure at which foaming does not occur at the flow front of the molten resin. Have been. In particular, it is effective for a thermoplastic resin that is not suitable for injection molding due to poor fluidity due to an excessively high molecular weight,
It is described that it is effective for improving the reproducibility of the mold surface, the glossiness, making the weld line inconspicuous, the reproducibility of a sharp edge on the mold surface, the reproducibility of fine irregularities on the mold surface, and the like. However, when carbon dioxide is absorbed or dissolved in a polyamide resin, the effect of lowering the viscosity due to carbon dioxide is smaller than that of other thermoplastic resins, and a method of lowering the viscosity when injection molding the polyamide resin, or It has been awaited to establish a composition of a polyamide-based resin exhibiting a viscosity reduction effect more remarkably.

[0019]

DISCLOSURE OF THE INVENTION The present invention does not limit the molecular weight of a polyamide (hereinafter abbreviated as "PA") resin, does not increase the resin temperature unnecessarily at the time of injection molding, and allows the PA resin to be melted. It is an object to make it possible to easily fill a mold cavity with a resin. Specifically, by facilitating filling of the mold cavity with the PA-based resin composition in a molten state, it is easier to fill the mold cavity as compared with a conventional PA-based resin, Another object of the present invention is to improve the precision generally required for PA-based resin molded products, and to enable application to injection molded products having thinner and more complicated shapes.

[0020]

Means for Solving the Problems The present inventors do not limit the molecular weight of polyamide (hereinafter abbreviated as "PA") based resins.
Without raising the resin temperature more than necessary during injection molding,
It is an object of the present invention to make it easier to fill a mold cavity with a PA resin in a molten state. In particular,
The present invention improves the precision of a molded product required for a PA resin by facilitating the filling of a mold cavity with a PA resin in a molten state. In order to make it possible to apply to injection molded products, we studied.

As a result, the polyamide resin composition comprises at least (A) the polyamide resin and at least one kind of fibrous (B) inorganic or organic filler. 1M in a molten state.
A polyamide-based resin composition molded article obtained by mixing carbon dioxide pressurized to Pa or more and then filling the mixture into a mold cavity is a conventional PA-based resin, for example, (A) It is easier to fill the mold cavity than PA resin, improves the precision generally required for PA resin molded products, injection molding with thinner and more complex shapes The present inventors have found that a problem that is likely to occur during the manufacture of a product is solved, and have completed the present invention.

That is, the present invention provides: The polyamide-based resin composition is a polyamide-based resin composition comprising at least (A) a polyamide-based resin and at least one kind of fibrous (B) inorganic or / and organic filler. The polyamide-based resin composition in a state, after mixing carbon dioxide pressurized to atmospheric pressure or more, a polyamide-based resin composition molded article characterized by being obtained by filling the mold cavity, 2. (A) The polyamide-based resin composition molded article according to the above (1), wherein the polyamide-based resin is a polyamide-based resin containing a polyamide 6-6 resin as a main component.

3. (A) The molded article of the polyamide-based resin composition as described in (1) above, wherein the polyamide-based resin is a polyamide / polyphenylene ether-based polymer alloy composed of at least a polyamide resin and a modified polyphenylene ether resin. 4. (1) wherein the filler (B) constituting the polyamide resin composition has an aspect ratio of 10 or more.
4. The molded article of the polyamide-based resin composition according to any one of 2. to 3., The above (1), wherein the filler (B) constituting the polyamide resin composition has an aspect ratio of 20 or more.
The molded article of the polyamide-based resin composition according to any one of claims 1 to 3,

6. 6. The molded article of the polyamide resin composition according to any one of the above items 1 to 5, wherein the fibrous filler (B) constituting the polyamide resin composition is a glass fiber. 7. The polyamide resin composition according to any one of the above items 1 to 6, wherein the amount of the fibrous filler (B) constituting the polyamide resin composition is 0.5% by weight or more. Molding,

8. The polyamide-based resin composition molded article has a foamed portion inside, and a non-foamed layer that is not substantially foamed on a surface layer portion of the molded article, wherein the molded article has a non-foamed layer. 8. A molded article of the polyamide-based resin composition according to any of the above, The polyamide-based resin composition molded article according to the above item 8, wherein the molded article of the polyamide-based resin composition has a non-foamed layer having a thickness of 500 μm or more in a surface layer portion of the molded article.

10. 10. The polyamide resin composition molded article according to any one of the above items 1 to 9, wherein the apparent specific gravity of the polyamide resin composition molded article is smaller than the specific gravity of the polyamide resin composition. The polyamide-based resin composition according to the above item 1, wherein the polyamide-based resin composition in a molten state is obtained by mixing carbon dioxide pressurized to an atmospheric pressure or higher and filling the mixture into a mold cavity. 11. an injection molding method for a resin composition molded article; The polyamide resin composition in a molten state
The method of injection-molding a polyamide-based resin composition molded article according to the above 1, wherein the method is obtained by mixing carbon dioxide pressurized to not less than MPa and filling the mixture into a mold cavity.

13. The polyamide-based resin according to the above 1, wherein the polyamide-based resin composition in a molten state is obtained by mixing carbon dioxide pressurized to 8 MPa or more and filling the mixture into a mold cavity. 13. an injection molding method of a composition molded article; 14. The method according to any of the above items 11 to 13, wherein the polyamide-based resin composition in a molten state is obtained by filling a mold cavity maintained or maintained at or above atmospheric pressure with a pressurized gas. Injection molding method of a molded article of a polyamide-based resin composition,

15. After filling the mixture of the polyamide resin composition and carbon dioxide into the mold cavity, the method has a step of maintaining the pressure under a pressure of 30% or more of the filling pressure for a certain period of time. 15. The injection molding method for a molded article of a polyamide-based resin composition according to any one of the above, After filling the mixture of the polyamide resin composition and carbon dioxide into the mold cavity, the method has the step of maintaining the pressure under a pressure of 150% or less of the filling pressure for a certain period of time. And an injection molding method of the molded article of the polyamide resin composition according to any one of the above.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. Polyamide (hereinafter referred to as “PA”) used in the present invention
(A) PA resin constituting the resin composition,
An amide bond {-NH-C (= O)-} is added to the polymer main chain.
Any one having the following can be used. Generally, the (A) PA resin is obtained by ring-opening polymerization of lactams, polycondensation of diamine and dicarboxylic acid, polycondensation of aminocarboxylic acid, and the like, but is not limited thereto.

The above-mentioned diamines are roughly classified into aliphatic, alicyclic and aromatic diamines. Specific examples include tetramethylene diamine, hexamethylene diamine, undecamethylene diamine, dodecamethylene diamine, tridecamethylene diamine, and the like. 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 5-methylnanomethylenediamine, 1,3-bisaminomethylcyclohexane, 1,4
-Bisaminomethylcyclohexane, m-phenylenediamine, p-phenylenediamine, m-xylylenediamine, p-xylylenediamine.

The dicarboxylic acids are roughly classified into aliphatic,
Alicyclic and aromatic dicarboxylic acids are mentioned, and specific examples are adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1,1,3-tridecandioic acid,
1,3-cyclohexanedicarboxylic acid, terephthalic acid,
Examples include isophthalic acid, naphthalenedicarboxylic acid, and dimer acid. As lactams, specifically, ε-
Caprolactam, enantholactam, ω-laurolactam and the like.

Examples of the aminocarboxylic acid include ε-aminocaproic acid, 7-aminoheptanoic acid, 8
-Aminooctanoic acid, 9-aminonanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, 13-aminotridecanoic acid and the like. In the present invention,
Any of these lactams, diamines, dicarboxylic acids, and ω-aminocarboxylic acids may be used alone or in the form of a mixture of two or more, and any of the copolymerized PAs obtained by polycondensation may be used.

Further, those obtained by polymerizing these lactams, diamines, dicarboxylic acids and ω-aminocarboxylic acids to a low molecular weight oligomer stage in a polymerization reactor and increasing the molecular weight by an extruder or the like can also be suitably used. it can. In particular, (A) PA resins that can be usefully used in the present invention include PA6, PA6-6, PA4-6, PA11, PA
12, PA6-10, PA6-12, PA-MXD, P
A6I, PA6T, PA6 / 6-6, PA6 / 6-1
2, PA6 / MXD, PA6T, PA6I, PA6 / 6
T, PA6 / 6I, PA6-6 / 6T, PA6-6 / 6
I, PA6 / 6T / 6I, PA6-6 / 6T / 6I, P
A6 / 12 / 6T, PA6-6 / 12 / 6T, PA6 /
12 / 6I and PA6-6 / 12 / 6I.

Also, PA resins obtained by copolymerizing a plurality of (A) PA resins with an extruder or the like can be used.
Preferred (A) PA-based resins are PA6, PA6-6, and mixtures thereof. Here, "PA-MXD"
Is PA obtained by polycondensation of meta-xylylenediamine and adipic acid. Specifically, PA-MXD6
And the like. “PA6I” is an aliphatic-aromatic PA obtained from hexamethylenediamine and isophthalic acid, and “PA6T” is an aliphatic-aromatic PA obtained from hexamethylenediamine and terephthalic acid.

The number average molecular weight of the (A) PA resin used in the present invention is preferably from 5,000 to 100,000, more preferably from 10,000 to 30,000. The (A) PA resin in the present invention is not limited to these, and may be a mixture of a plurality of PA resins having different molecular weights. For example, a number average molecular weight of 10,000
A mixture of a low molecular weight PA of 0 or less and a high molecular weight PA of 30,000 or more, a mixture of a low molecular weight PA having a number average molecular weight of 10,000 or less and a general PA of about 15,000, and the like.

The PA end groups participate in the reaction with the functionalized polyphenylene ether. PA generally has an amino group and a carboxyl group as a terminal group. Generally, when the carboxyl group concentration exceeds the amino group concentration, the impact resistance generally decreases, the flowability increases, and conversely, When the amino group concentration exceeds the carboxyl group concentration, the impact resistance is improved and the fluidity is reduced. These preferred ratios are 9/1 to 1/9, more preferably 8/2 to 1/9, and even more preferably 6/4 to 1/9, in terms of amino group / carboxyl group ratio.

The concentration of the terminal amino group is preferably at least 10 meq / kg. More preferably, it is 30 meq / kg or more. As a method for adjusting the terminal group of the (A) PA-based resin, a known method that is apparent to those skilled in the art may be used. For example, P
During the polymerization of A, addition of diamines or dicarboxylic acids, addition of monocarboxylic acids and the like can be mentioned. Also, (A) PA
For the purpose of improving the heat stability of the resin, a metal stabilizer may be used.

Specific examples of the metal-based stabilizer include CuI,
Examples thereof include CuCl ₂ , copper acetate, potassium iodide, and cerium stearate, and these may be used in combination.
The preferred compounding amount of the metal-based stabilizer is 0.001 to 1 part by weight based on 100 parts by weight of the PA-based resin. Further, the (A) PA-based resin in the present invention may be a polymer alloy obtained by mixing one or more resins having the above-described PA component as a main component and having different characteristics.

There are no particular restrictions on the resins having different properties that can be used by mixing with the (A) PA resin as the main component as long as they are compatible with the (A) PA resin as the main component. Without, for example, polyacetal, polyethylene terephthalate, polybutylene terephthalate, various polyethylene, polyetheretherketone, polypropylene,
Polystyrene, ABS resin, polyvinyl chloride, polycarbonate, polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polyimide,
Examples thereof include polyamideimide, polyetherimide, polyarylate, polysulfone, polyethersulfone, polyetheretherketone, liquid crystal polymer, polytetrafluoroethylene, thermoplastic elastomer, polytetrafluoroethylene, and polyvinyl alcohol.

In particular, PA / PPE polymer alloys composed of at least PA resin and polyphenylene ether resin or modified polyphenylene ether resin have lower specific gravity and higher heat resistance than PA resin. It is preferable because it has a feature that it is easy to make it flame-retardant with a specific halogen-based flame retardant. Here, the modified polyphenylene ether resin refers to a resin composition obtained by modifying a polyphenylene ether resin with a styrene-based compound, a rubbery polymer, or the like, and the styrene-based compound specifically refers to polystyrene, rubber reinforced Polystyrene, acrylonitrile / styrene copolymer,
Examples thereof include acrylonitrile / butadiene / styrene copolymer and other styrene copolymers.

The PA resin composition used in the present invention comprises:
It is a PA-based resin composition comprising at least (A) a PA-based resin and (B) a fibrous inorganic or / and organic filler. This is a mixture of (A) a PA-based resin composition in which a (B) fibrous inorganic or / and organic filler is added to a PA-based resin, and carbon dioxide pressurized to 1 MPa or more. This is because the viscosity of (A) shows a lower value than the viscosity of the (A) PA resin.

Therefore, as compared with (A) PA resin, the PA resin composition of the present invention can be easily filled into the mold cavity by mixing with carbon dioxide pressurized to 1 MPa or more. It is believed that it is possible to improve the precision required for PA-based resin molded products, and to solve the problems that are likely to occur during the production of injection molded products having thinner and more complex shapes.

The filler (B) used in the present invention is characterized by having a fibrous shape. This is because the filler (B) is fibrous, so that 1M of the filler is contained in the PA resin composition.
This is because the effect of lowering the viscosity at the time of injection molding is increased by effectively dispersing the carbon dioxide pressurized to Pa or more as a plasticizer. The filler (B) is characterized in that it is fibrous, and its aspect ratio is preferably 10 or more, and more preferably 20 or more.

Here, the aspect ratio is the aspect ratio of the filler (B). A large aspect ratio means that
This indicates that the overall length is larger than the diameter. The filler (B) used in the present invention is characterized by being inorganic or / and organic. The filler (B) is not compatible with the PA resin composition during injection molding of the PA resin composition according to the present invention, does not decompose the PA resin composition, and (B) the filler It is necessary that the substance itself does not decompose or melt.

Specifically, glass fiber, carbon fiber, metal fiber, aramid fiber, potassium titanate, asbestos,
Silicon carbide, ceramic, silicon nitride, barium sulfate,
Calcium sulfate, kaolin, clay, pyrophyllite, bentonite, sericite, zeolite, mica,
Mica, nepheline sinite, talc, atalpargite, wollastonite, slag fiber, ferrite, silicon, calcium, calcium carbonate, magnesium carbonate,
Dolomite, zinc oxide, gypsum, glass beads, glass powder, glass balloon, quartz, quartz glass, alumina, barium sulfate, red iron, tungsten and the like can be considered.

Further, two or more kinds of the above-mentioned inorganic or organic fillers can be used in combination. Further, if necessary, it can be used after being pre-treated with a silane-based or titanium-based coupling agent. PA of the present invention
Although the amount of the filler (B) added to the PA-based resin composition is not limited, carbon dioxide pressurized to an atmospheric pressure or higher can be easily mixed into the PA-based resin composition, and the PA-based resin composition can be efficiently used. For dispersion, the amount is preferably 0.5% by weight or more, more preferably 1.0% by weight or more. When the amount is less than 0.5% by weight, P
(B) is not preferable because it is difficult to uniformly disperse (B) in the A-based resin composition.

Here, (B) the amount of filler added is defined as PA
The ratio when the total amount of the resin is 100% by weight,
(B) When two or more fillers are used, the total amount of the fillers is referred to. In the present invention, the added amount of the filler (B) refers to the amount added when only one kind of inorganic filler is added, and refers to the total added amount when two or more kinds of inorganic fillers are added. Further, the amount of the filler (B) indicates a ratio when the total amount of the PA-based resin composition is 100% by weight.

In the PA resin composition of the present invention, additives usually used, such as antioxidants, flame retardants, release agents, lubricants, heat stabilizers, weather resistance stabilizers, rust inhibitors, Filler, colorant, antibacterial agent, fungicide, etc.
More than one kind can be added. Further, by selecting one or more of carbon fiber, metal fiber, and graphite as other additives, the electric resistance value of the crystalline resin can be reduced. This is preferable because a small powder such as dust can be prevented from being attached to the PA-based resin composition molded article by static electricity.

In the present invention, a PA-based resin composition molded article is obtained by mixing carbon dioxide pressurized at or above atmospheric pressure with a PA-based resin composition in a molten state and then filling the mixture into a mold cavity. It is characterized by being able to. this is,
By dissolving or absorbing carbon dioxide pressurized above atmospheric pressure in the PA-based resin composition, the viscosity of the PA-based resin composition decreases, and the fluidity when filling the mold cavity is improved. It is. This is presumed to be because carbon dioxide is efficiently dispersed as a plasticizer when carbon dioxide is dissolved or absorbed in the PA-based resin in a molten state.
As a result, the mold cavity can be easily filled as compared with a conventional PA resin, for example, (A) PA resin.

For this reason, the means for improving the precision required for the PA-based resin composition molded article and solving the problems which are likely to occur during the production of injection molded articles having a thinner and more complicated shape are solved. This is preferable because it is not necessary to raise the resin temperature, so that there is no need to worry about thermal decomposition and deterioration of the resin, and it is not necessary to raise the mold temperature more than necessary. Further, since the filling pressure at the time of filling the mold cavity with the PA-based resin composition is reduced, deformation of the molded product such as warpage after molding is less than that of the conventional molding method. This is considered to be due to the fact that the filling pressure during filling into the mold cavity is lower than that of the conventional molding method, so that residual strain hardly remains in the molded product. This facilitates injection molding with a PA-based resin composition having a high viscosity at the time of melting, improves the quality of molded products, increases the degree of freedom in product design, and has a high viscosity at the time of melting. It is expected that a PA resin composition that could not be realized, particularly an injection molded article using a PA resin composition using a PA resin having a high molecular weight, can be expected.

The molded article of the PA-based resin composition of the present invention is prepared by mixing carbon dioxide pressurized at atmospheric pressure or higher with the PA-based resin composition in a molten state and then filling the mixture into a mold cavity. Although it is characterized by being obtained, in order to further increase the effect of lowering the viscosity due to carbon dioxide, it is preferable to mix carbon dioxide pressurized to 4 MPa or more with the PA-based resin composition in a molten state, 8
More preferably, it is carbon dioxide pressurized to MPa or more.

The method of dissolving or absorbing carbon dioxide pressurized at atmospheric pressure or higher into the PA-based resin composition in a molten state is not limited. Easy to disperse evenly in the material, easy to dissolve or absorb in a short time, easy to adjust absorption or dissolution amount, easy setup before molding, molding machine hopper, etc. Considering that there is no need to perform, by providing a facility for carbon dioxide supply in the heating cylinder of the injection molding machine, at the nozzle of the molding machine, or at any position between the nozzle of the molding machine and the mold It is preferable to dissolve or absorb carbon dioxide in the PA-based resin composition in a molten state.

A method of dissolving or absorbing carbon dioxide in a PA resin in a molten state in a heating cylinder of an injection molding machine, at a nozzle of the molding machine, or at any position between the nozzle of the molding machine and a mold. As a method, a method of supplying carbon dioxide pressurized to an atmospheric pressure or higher to the PA-based resin composition in a molten state from an intermediate portion or a tip portion of a screw of a molding machine or a heating cylinder may be considered. When supplying carbon dioxide from the screw of the molding machine or the middle part of the heating cylinder, increase the depth of the screw groove near the carbon dioxide supply part like the vent of a vent type screw, and It is preferable that the resin pressure is lowered and the resin transfer is starved. Also, after supplying carbon dioxide, a screw is provided with a mixing mechanism such as a dalmage or a kneading pin to uniformly dissolve or absorb and disperse in the PA-based resin composition, and a static mixer is provided in the resin flow path. Can be considered.

In the present invention, the PA-based resin composition molded product is characterized by having a foamed portion inside, and the foamed portion has a cross-section of the molded product of 10 to 2 measured by an optical microscope or the like.
When observed at a magnification of 0 times, the void due to foaming, or
It indicates the part where the whitening phenomenon is confirmed. Since the PA-based resin composition molded article in the present invention has a foamed portion inside, the resin section has a substantially thinner thickness than the product thickness, and the volume shrinkage is reduced. Is considered to have excellent long-term dimensional accuracy and dimensional stability.

Further, since the volume shrinkage of the PA resin is compensated for from the inside of the molded article by forming a foamed portion inside the molded article, the occurrence of sink marks on the surface of the molded article is suppressed. It seems to have been. In the present invention, PA
The system resin composition molded article has a foamed part inside, and
The molded article has a non-foamed layer having a thickness of 500 μm or more on the surface layer portion.
If the thickness is less than 0 μm, the surface of the molded article may be swollen, and the mechanical strength may be decreased.

The thickness of the non-foamed layer can be adjusted by the holding pressure and the holding time. The higher the holding pressure and the longer the holding time, the thicker the non-foamed layer tends to be. But,
If the holding pressure is too high or if the holding time is too long,
When the PA resin cools and solidifies in the mold cavity,
Carbon dioxide dissolved in the PA-based resin is not preferable because it does not easily form a foamed portion inside the molded article and may cause sink on the surface of the molded article.

This is because when the PA resin is dissolved or absorbed in the PA resin and then filled into the mold cavity, the PA resin is cooled and solidified in the mold cavity to cause volume shrinkage. This is because carbon dioxide dissolved or absorbed in the PA-based resin is formed by appropriately foaming. By having a foamed portion inside the PA-based resin composition molded article, it becomes possible to apply the molded article with the thermoplastic resin composition to a thicker molded article,
It is expected that the degree of freedom in product design will increase.

The amount of dissolving or absorbing the carbon dioxide in the PA resin is not limited. However, by dissolving or absorbing the carbon dioxide in the PA resin, the PA resin is filled into the mold cavity. The dissolution or absorption amount is preferably 0.2% by weight or more, and more preferably 0.4% by weight or more, since the fluidity at the time of dissolving is improved and an increase in the filling pressure can be suppressed. More preferred.
If the amount of carbon dioxide dissolved or absorbed is less than 0.2% by weight, it is difficult to obtain the effect of improving the fluidity by dissolving or absorbing carbon dioxide, and sufficient dimensional accuracy and dimensional stability are obtained. It is not preferable because it becomes difficult to obtain.

In the present invention, the amount of dissolved or absorbed carbon dioxide is measured by the following method. (1) Immediately after molding, measure the weight of the molded article (M1). (2) The molded article is left in a vacuum dryer kept at 100 ° C. for 48 hours or more in a state where the pressure is equal to or lower than the atmospheric pressure, preferably in a state where the pressure is closer to vacuum, and after the carbon dioxide is diffused, The weight of the molded product taken out of the vacuum dryer is measured (M2). (3) The amount of carbon dioxide dissolved or absorbed (% by weight)
It is calculated from (M1−M2) ÷ M2 × 100.

Normally, the injection molding method has a step of filling the resin into the mold cavity and then holding the resin in the cavity under pressure. This step is referred to as a "holding step", and the degree of the pressure is referred to as "holding pressure". In the injection molding method of the PA-based resin according to the present invention, after filling the PA-based resin into the mold cavity, the filling pressure is reduced. It is preferable to hold the resin in the mold cavity under pressure by a pressure corresponding to 30% or more. In the present invention, the holding pressure is 30% of the filling pressure.
If it is less than 1, the thickness of the non-foamed layer formed on the surface layer of the molded article becomes thin, and the proportion of the foamed portion in an arbitrary cross section becomes large.

Here, the filling pressure refers to a resin pressure generated when filling a molten resin into a mold cavity. Specifically, the screw position in the in-line screw type injection molding machine, and the plunger position in the pre-plasticity type injection molding machine, are the maximum values of the resin pressure generated when moving from the measuring position to the VP (holding pressure) switching position. Point to. Also, the pressure holding time is not limited, but when the pressure holding time is extremely short, the carbon dioxide dissolved or absorbed in the crystalline resin before filling into the mold cavity expands, It is not preferable because a swelling phenomenon may occur in the molded product.

Specifically, the dwell time is preferably at least 3 seconds, more preferably at least 5 seconds,
Most preferably, it is at least 7 seconds. P in the present invention
The apparent specific gravity of the molded article of the A-based resin composition is preferably in the range of 95 to 99.5%, more preferably in the range of 96 to 99.5% of the specific gravity of the PA-based resin, and 98. Most preferably, it is in the range of ９９99.5%.

This is because the apparent specific gravity of the molded product is different from that of the PA.
When the specific gravity of the resin is 95% or less, it means that the proportion of the foamed portion inside the molded article is too large, and the decrease in strength of the molded article cannot be ignored. When the apparent specific gravity exceeds 99.5% of the specific gravity of the PA-based resin, it means that the foamed portion is not sufficiently formed inside the molded product, and sinks occur on the surface of the molded product. It seems that the internal foamed portion does not exist effectively.

The fact that the apparent specific gravity of the PA-based resin composition molded article in the present invention is in the range of 95 to 99.5% of the specific gravity of the PA-based resin to be used means that the foamed portion has a moderately foamed part inside the molded article. It is considered to be in the range of apparent specific gravity present. By having a foamed portion inside the PA-based resin composition molded article, it is possible to apply the PA-based resin composition molded article to a thicker molded article, and it is expected that the degree of freedom in product design is increased. .

The PA-based resin composition molded article of the present invention is a molded article, part, or product in the minimum unit composed of the PA-based resin, such as automobiles, electronic products, containers, household goods,
It refers to the smallest unit of molded products, parts and products made of PA resin used for electrical products, general machinery, piping parts, precision machinery, tools, industrial parts, transportation equipment, etc. In addition to secondary processing such as sheets and plates Including molded products and products. In the present invention, the injection molding method of the PA-based resin composition is a usual molding and processing method of a thermoplastic resin. In addition to the most common injection molding method, a hollow injection molding method and a gas assist molding method , Blow molding, injection / compression molding and the like.

In the injection molding method of the PA-based resin composition molded article of the present invention, the P
When filling the mold resin cavity with the A-based resin composition, if the amount of dissolved or absorbed carbon dioxide is a certain value or more, a foamed pattern may be generated on the surface of the molded product. In order to suppress the occurrence of a foaming pattern on the surface of the molded product, the inside of the mold cavity must be adjusted or maintained by a pressurized gas at a pressure higher than the pressure at which foaming does not occur at the flow front of the PA resin composition. is necessary.

The pressure of the pressurized gas may be a minimum pressure at which the foaming pattern on the surface of the molded product disappears. The amount of gas used during the molding cycle is minimized, and the sealing of the mold cavity and the gas supply device are performed. In order to simplify the structure of the above, it is preferable that the gas pressure is low. If the gas pressure exceeds 15 MPa, the mold may open due to the gas pressure, and problems such as difficulty in sealing the mold cavity may easily occur. Therefore, it can be said that the pressure of the gas for pressurizing the mold cavity is preferably not lower than atmospheric pressure and not higher than 15 MPa.

At this time, as the gas for adjusting or maintaining the inside of the mold cavity to a constant pressure, a single substance or a mixture of various gases inert to the PA resin composition can be used. P
Carbon dioxide and hydrocarbons having a high solubility in the A-based resin composition, and gases in which hydrogen has been partially replaced with fluorine are preferred. Further, in consideration of the fact that a gas having a high purity can be obtained relatively inexpensively although the solubility in the PA-based resin composition is low, it is also possible to use nitrogen gas.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following. The resin used in the examples and comparative examples was PA6-6 resin ("Leona 1300S, 13G1" manufactured by Asahi Kasei Corporation).
5 "), each of which is in the form of a pellet before molding. The above-mentioned "Leona 1300S" is a general PA6-6 resin widely used for injection molding, and does not contain an inorganic or organic filler.

"Leona 13G15" is a PA resin composition obtained by adding long glass fibers to a PA6-6 resin equivalent to "Leona 1300S" described above, and the added amount is 15% by weight. Composition A was composed of 99.0% by weight of a PA6-6 resin (equivalent to the above “Leona 1300S”) and 1.0% of glass fibers having an aspect ratio of 40.
It is a PA resin composition by weight%.

Composition B was prepared by mixing PA6-6 resin (same as above) with 9
The PA resin composition is composed of 7.0% by weight and 3.0% by weight of glass fibers having an aspect ratio of 30. Composition C is a PA-based resin composition comprising 95.3% by weight of PA6-6-based resin (same as above) and 4.7% by weight of glass fiber having an aspect ratio of 30. Composition D is a PA-based resin composition comprising 90% by weight of a PA6-6-based resin (same as above) and 10% by weight of a glass fiber having an aspect ratio of 40.

Compositions A, B, C, and D were used in each of Examples and Comparative Examples by using a mixture obtained by kneading a PA6-6 resin and glass fiber and then processing the mixture into pellets. The viscosity was measured using the viscosity meter shown in FIG. 1 according to the following procedure. At this time, the shear rate γ during viscosity measurement
a (/ sec) was in the range of 1.0 × 10 ³ to 1.0 × 10 ⁶ .

(1) The temperature of the heating cylinder and the plunger of the viscometer is set at 278 ° C. and maintained. (2) An appropriate amount of the PA-based resin composition in a molten state or a mixture of the PA-based resin composition and pressurized carbon dioxide is measured on a plunger portion, and an injection speed S appropriately set.
Inject through the orifice at a (mm / sec). At this time, the resin pressure Pa (Pa) is measured by a pressure sensor. The length La of the orifice used here is 10 mm,
The orifice hole diameter Da is 1.0 mm.

(3) From equations 2 and 3 shown below, τ
a and γa are calculated. Shear stress τa (Pa) = (Pa × Da) ÷ (4 × La) (Formula 2) Shear rate γa (/ sec) = (4 × Qa) ÷ (π × Da ³ ÷ 8) (Formula 3) , Qa (mm ³ / sec) = (π × Da ² ) ÷ 4 ×
Sa. (4) Calculate the viscosity ηa from Equation 4 shown below. Viscosity ηa (Pa · sec) = shear stress ÷ shear rate = τa ÷ γa (Equation 4)

[0075]

Example 1 A composition A in a molten state heated to 278 ° C. and carbon dioxide pressurized to 12.2 MPa were sufficiently mixed, and then supplied to a plunger section of a viscosity measuring device to obtain composition A. And the viscosity of the mixture of carbon dioxide were measured. Table 1 shows the results.

[0076]

Examples 2-3 After heating to 278 ° C. and sufficiently mixing the composition B in a molten state with carbon dioxide pressurized to 8.2 MPa and 12.0 MPa, the mixture was placed in a plunger section of a viscosity measuring device. The mixture was supplied, and the viscosity of the mixture of the composition B and carbon dioxide was measured. Table 1 shows the results.

[0077]

Example 4 A composition C in a molten state heated to 278 ° C. and carbon dioxide pressurized to 12.2 MPa were sufficiently mixed, and then the mixture was supplied to a plunger part of a viscometer to obtain a composition C. And the viscosity of the mixture of carbon dioxide were measured. Table 1 shows the results.

[0078]

Example 5 A composition D in a molten state heated to 278 ° C. and carbon dioxide pressurized to 12.0 MPa were sufficiently mixed, and the mixture was supplied to a plunger part of a viscosity measuring device. And the viscosity of the mixture of carbon dioxide were measured. Table 1 shows the results.

[0079]

Embodiment 6 After sufficiently mixing Leona 13G15 in a molten state heated to 278 ° C. and carbon dioxide pressurized to 12.2 MPa, the mixture is supplied to a plunger section of a viscosity measuring device, and Leona 13G15 and the carbon dioxide are mixed. The viscosity of the mixture of carbon was measured. Table 1 shows the results.

[0080]

Comparative Example 1 Leona 1300S in a molten state heated to 278 ° C. was supplied to a plunger part of a viscosity measuring device, and the viscosity was measured.

[0081]

COMPARATIVE EXAMPLE 2 Leona 1300S in a molten state heated to 278 ° C. and carbon dioxide pressurized to 3.8 MPa were sufficiently mixed, and then supplied to a plunger section of a viscosity measuring device, and Leona 1300S and carbon dioxide were mixed. The viscosity of the mixture of carbon was measured.

[0082]

Comparative Example 3 A composition B in a molten state was heated to 278 ° C. and supplied to a plunger section of a viscosity measuring device, and the viscosity was measured. Table 1 shows the results.

[0083]

[Table 1]

[0084]

The molded article of the present invention can easily fill a mold cavity with a polyamide resin in a molten state without limiting the molecular weight of the polyamide resin and without unnecessarily increasing the resin temperature during injection molding. It is possible to obtain by doing.

[Brief description of the drawings]

FIG. 1 shows a model diagram of a viscometer.

[Explanation of symbols]

 1 orifice 2 pressure sensor 3 plunger

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme court ゛ (Reference) // B29K 77:00 B29K 77:00 105: 04 105: 04 105: 08 105: 08 105: 16 105: 16 F term (reference) 4F071 AA51 AA54 AB01 AB17 AD01 AD06 AE01 AE17 BB05 BC17 4F206 AA29 AB11 AB16 AB19 AB25 AG20 AR027 JA04 JF02 JF06 JF21 JF41 JL02 JM04 JM05 JN11 JN21 4J002 BB022 CB122 CF02 BD022 CF03 CL011 CL031 CL051 CL063 CM042 CM052 CN012 CN032 DA016 DA066 DE106 DE116 DE186 DE236 DE266 DG046 DG056 DJ006 DJ026 DJ036 DJ046 DJ056 DL006 DM006 FA043 FA046 FD013 FD016

Claims (16)

[Claims] 1. A polyamide resin composition comprising a polyamide resin composition comprising at least (A) a polyamide resin and at least one kind of a fibrous (B) inorganic or / and organic filler. And a polyamide resin obtained by mixing the polyamide resin composition in a molten state with carbon dioxide pressurized at atmospheric pressure or higher, and then filling the mixture into a mold cavity. Composition molded articles. 2. The polyamide resin composition molded article according to claim 1, wherein the polyamide resin (A) is a polyamide resin containing a polyamide 6-6 resin as a main component. 3. The polyamide resin according to claim 1, wherein the polyamide resin (A) is a polyamide / polyphenylene ether polymer alloy composed of at least a polyamide resin and a modified polyphenylene ether resin. Composition molded articles. 4. The molded article of the polyamide resin composition according to claim 1, wherein an aspect ratio of the filler (B) constituting the polyamide resin composition is 10 or more. 5. The polyamide resin composition molded article according to claim 1, wherein an aspect ratio of the filler (B) constituting the polyamide resin composition is 20 or more. 6. The polyamide resin composition according to claim 1, wherein the fibrous (B) filler constituting the polyamide resin composition is a glass fiber. Goods. 7. The filler according to claim 1, wherein the amount of the fibrous filler (B) constituting the polyamide resin composition is 0.5% by weight or more. A molded article of a polyamide-based resin composition. 8. A molded article of a polyamide-based resin composition, which has a foamed portion inside and a non-foamed layer which is not substantially foamed on a surface layer of the molded article.
A molded article of the polyamide-based resin composition according to any one of claims 1 to 7. 9. The polyamide resin molded article according to claim 8, wherein the polyamide resin composition molded article has a non-foamed layer having a thickness of 500 μm or more on the surface layer of the molded article. . 10. The polyamide resin composition according to claim 1, wherein an apparent specific gravity of the molded product of the polyamide resin composition is smaller than a specific gravity of the polyamide resin composition. Goods. 11. The method according to claim 1, wherein said polyamide resin composition in a molten state is obtained by mixing carbon dioxide pressurized at atmospheric pressure or higher and filling the mixture into a mold cavity. 2. The injection molding method of the polyamide resin composition molded article according to 1. 12. The method according to claim 1, wherein the polyamide resin composition in a molten state is obtained by mixing carbon dioxide pressurized to 4 MPa or more and filling the mixture into a mold cavity. The injection molding method of the polyamide resin composition molded article according to the above. 13. The method according to claim 1, wherein the polyamide resin composition in a molten state is obtained by mixing carbon dioxide pressurized to 8 MPa or more and filling the mixture into a mold cavity. The injection molding method of the polyamide resin composition molded article according to the above. 14. The method according to claim 11, wherein the polyamide resin composition in a molten state is obtained by filling a mold cavity maintained or maintained at a pressure higher than the atmospheric pressure with a pressurized gas. 14. The injection molding method for a molded article of a polyamide-based resin composition according to any one of 13). 15. After filling a mixture of a polyamide resin composition and carbon dioxide into a mold cavity, the mixture is charged at a filling pressure of 3%.
The injection molding method for a molded article of a polyamide-based resin composition according to any one of claims 11 to 14, further comprising a step of maintaining the pressure under a pressure of 0% or more for a predetermined time. 16. After filling a mixture of a polyamide resin composition and carbon dioxide into a mold cavity, the mixture is filled at a filling pressure of 1%.
The injection molding method for a molded article of a polyamide-based resin composition according to any one of claims 11 to 14, further comprising a step of maintaining the pressure under a pressure of 50% or less for a predetermined time.