JP2508565B2 - Composite resin molding structure and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite resin molding structure having a multi-layered distribution structure using a liquid crystal polyester and a method for producing the same, and more particularly, it has improved melt moldability and gas permeation resistance. The present invention relates to a liquid crystal resin molding structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art Resin molded products, especially containers, are widely used as packaging containers for foods, cosmetics, detergents and various chemicals because they are lightweight and have excellent impact resistance.

However, in metal cans and glass bottles, the gas permeation through the vessel wall is almost zero, whereas in the case of the resin molded container, the gas permeation through the vessel wall is in an order that cannot be ignored. The problem is that it occurs. In order to improve this problem, it has already been performed to use a gas permeation-resistant resin as a container constituent material, and for example, ethylene-vinyl alcohol copolymer or vinylidene chloride-based resin has a gas permeation resistance of the container wall. Used for improvement purposes.

However, the ethylene-vinyl alcohol copolymer exhibits an excellent gas barrier property under the condition that the relative humidity (RH) is 0%, but under the high humidity condition, the gas permeation coefficient, for example, Po ₂ increases by about two digits. There is an inconvenience to do. Further, the vinylidene chloride-based resin has an advantage that the gas permeability coefficient has a small humidity dependency, but has a problem in its thermal stability and is often restricted in forming the container and in using the container.

In recent years, liquid crystal polymers have attracted attention in the field of fibers due to their excellent mechanical properties. This liquid crystal polymer includes one that forms a liquid crystal in a solution (dope) state (lyotropic) and one that forms a liquid crystal in a molten state (thermotropic). The former is represented by Kevlar (DuPont). And the latter is an aromatic polyester typified by Vectra (Celanese Company).

These liquid crystals form a so-called polydomain structure in which domains in which rigid molecules are regularly arranged are continuous, and by applying shear stress to them, these molecules are oriented in the direction in which shear stress is applied. It is said that excellent strength can be obtained.

It has already been proposed to use a liquid crystalline polyester for the production of stretched molded products such as films. For example, JP-A-62-187033 discloses an aromatic dicarboxylic acid unit (A) and an aliphatic diol unit. (B) and a layer formed of a thermo-liquid crystalline polyester formed of a hydroxy aromatic carboxylic acid unit (C) and a layer formed of a polyester containing a polyethylene terephthalate component on at least one surface thereof, and at least in one direction Laminated stretch molded articles characterized by being oriented are described.

JP-A-3-201 proposed by the present inventors
No. 4 publication describes polyethylene terephthalate (PET).
In the thermoplastic resin and the liquid crystal polyester and the content was and thermoplastic melting point and a temperature range of more than 10 ° C. than the temperature of either the high temperature side of the flow temperature of the liquid crystal polyester resin etc., shear rate 1 × 10 ⁴ sec ^{- A} mixture in which the melt viscosity of the thermoplastic resin measured under ^one or more conditions is larger than the melt viscosity of the liquid crystal polyester is melt-injected at a resin temperature that gives the above-mentioned difference in melt viscosity in an injection mold for container molding, mainly inside and outside. Described is a method for producing a liquid crystal polyester container having excellent gas permeation resistance, which is characterized by forming a multi-layer distribution structure consisting of a distributed thermoplastic resin and a liquid crystal polyester mainly distributed on the intermediate side in a mold. There is.

[0009]

However, in the melt molding of a liquid crystal polyester into a three-dimensional structure such as a three-dimensional container, the polyester molecules tend to be oriented in the direction in which shear stress is applied, and therefore the molding itself is considerably difficult. There is a problem that it is difficult. That is, the melt of the liquid crystal polyester has a very large melt flow orientation unlike the melt of the ordinary plastic, so that the melt tends to flow in a one-dimensional manner and is uniformly distributed in the die orifice. Is difficult to obtain, and it is difficult to obtain a molded product having a uniform wall thickness. Such a tendency is similarly observed in the case of extrusion molding or injection molding of a liquid crystal polyester and a normal polyester into a multilayer container.

If the liquid crystal polyester layer has such a non-uniform thickness or a portion where the layer itself is missing,
The inherent strength and gas permeation resistance of the liquid crystal polyester will be impaired.

Although melt-molding a liquid crystal polyester blended with PET certainly improves the above-mentioned drawbacks, as is known per se, PET has a large drawdown property in extrusion molding and the like. Is a drawback,
A blend of PET with liquid crystal polyester has a drawback that the drawdown tendency becomes significantly large due to the melt flow orientation tendency of the liquid crystal polyester. Thus, the methods found in the above prior art, although applicable to injection molding, are not applicable to extrusion or extrusion blow molding.

Molding structure of a container or the like whose liquid crystal polyester or a resin composition containing a liquid crystal polyester has poor melt moldability, that is, drawdown property, and whose size and shape are strictly controlled by extrusion molding or extrusion blow molding. It is desirable that a molded product can be produced, because the molded structure can be provided with excellent gas permeation resistance, heat resistance, mechanical strength, and the like, which the liquid crystal polyester originally has.

Therefore, the object of the present invention is to solve the above-mentioned drawbacks that occur when a liquid crystal polyester or a resin composition containing a liquid crystal polyester is melt-molded, and to improve the drawdown property and excessive one-dimensional flow tendency during melt molding. Moreover, it is another object of the present invention to provide a molding method capable of expressing a multi-layer distribution structure in a molded structure by molding the blend.

Another object of the present invention is to form a multi-layered distribution structure of a liquid crystal polyester and an olefin resin in a molded article while being formed from a blend of a liquid crystal polyester and an olefin resin, particularly high density polyethylene. The present invention provides a molded structure excellent in gas permeation resistance, heat resistance, mechanical strength and the like, and a method for manufacturing the same.

[0015]

According to the present invention, a layer formed by melt molding of a blend containing an olefin resin and a liquid crystal polyester, and containing the liquid crystal polyester preferentially, and the olefin resin is prioritized. There is provided a composite resin molding structure characterized by exhibiting a multi-layered distribution structure with layers that are included therein.

According to the present invention, the melt flow rate of the olefin resin and the liquid crystal polyester contained in a weight ratio of 95: 5 to 5:95 and measured at a temperature 10 ° C. higher than the high temperature side of the flow initiation temperature. (MFR) melts the blend having a range of 0.01 to 100 g / min, and the shear rate is measured separately under the condition that the shear rate is 10 ° C. higher than either high temperature side of the flow start temperature, Provided is a method for producing a composite resin molding structure having a multi-layer distribution structure, which is characterized in that melt molding is carried out under the condition that the absolute value of the difference between the melt viscosity of an olefin resin and the melt viscosity of a liquid crystal polyester is 1000 poise or less. .

The olefin resin and the liquid crystal polyester are contained in the blend in a ratio of 95: 5 to 5:95, particularly 90:10.
Preferably, the layer containing olefin resin preferentially is the inner and outer surface layers, and the layer containing liquid crystal polyester preferentially is the intermediate layer. Further, the most excellent effect can be obtained when the olefin resin is high density polyethylene.

[0018]

The first feature of the present invention is that the liquid crystal resin and the olefin resin are melt-molded in the form of a blend. When an olefin resin is blended with a liquid crystal polyester, its melt moldability is improved, and, for example, in the case of extrusion molding, the drawdown property found in a conventional liquid crystal polyester or a liquid crystal polyester-containing resin composition is remarkably improved. I found out.

Even in the case of injection molding, since the melt of liquid crystal polyester and its blend has a very large melt flow orientation, this melt tends to flow in a one-dimensional manner. However, there is a problem that it is difficult to obtain a molded product with a uniform thickness, and it is difficult to obtain a molded product with a uniform thickness. However, when a blend of a liquid crystal resin and an olefin resin is used for injection molding, It is possible to manufacture a molded product with high accuracy according to the shape and size.

According to the present invention, a molded article having excellent reproducibility of shape and dimensions can be obtained as described above. At the same time, a layer containing a liquid crystal polyester preferentially and an olefin resin are preferentially contained in the molded article. The second characteristic is that a multi-layered distribution structure with the layer included in is developed. That is, in the molded structure of the present invention, both resins are molded uniformly in the form of a blend, but both resins have a layered distribution structure.

The molded structure of the present invention can remarkably improve the barrier property (gas permeation resistance) against water vapor and oxygen by adopting the above-mentioned multilayer distribution structure.

The gas permeability coefficient of liquid crystal polyester is QL,
When the gas permeability coefficient of the olefin resin is QO, the gas permeability coefficient of the molded product is Q, and the volume fraction of the liquid crystalline polyester in the molded product is VL, the volume fraction of the olefin resin is VO, both resin components are homogeneous. When present in the form of a blend, the gas permeability of this article is

[Equation 1] Q = QL * VL + QO * VO, which is the arithmetic mean value, whereas in the case of a multilayer structure in which both resins are separated, the formula is

[Equation 2] 1 / Q = VL / QL + VO / QO, which is a harmonic mean value. Thus, when the liquid crystal polyester having excellent gas permeation resistance is distributed in layers,
The fact that the gas permeation resistance is remarkably improved becomes clear.

Further, it is obvious to those skilled in the art that if the liquid crystal polyester is formed into a layer, the mechanical properties and heat resistance of the liquid crystal polyester are strongly reflected in the molded product, as compared with the molded product in a homogeneous blend state. Will.

In the present invention, it is particularly preferable that the layer containing the olefin resin preferentially serves as the inner and outer surface layers and the layer containing the liquid crystal polyester preferentially serves as the intermediate layer. I mean,
This is because the olefin resin as the inner and outer surface layers protects the liquid crystal polyester layer, which is important in terms of gas permeation resistance, mechanical properties, heat resistance, etc., and prevents the formation of cracks and pinholes.

In order to produce the above-mentioned molded article having a multi-layered distribution structure, an olefin resin and a liquid crystal polyester are mixed at 95: 5.
To 5:95, especially 90:10 to 10:90 by weight, and has a melt flow rate (MFR) of 0.01 measured at a temperature 10 ° C. higher than the high temperature side of the flow initiation temperature.
To 100 g / min, especially 0.1 to 90 g / min
Melt of the olefin resin and the melting of the liquid crystal polyester by melting the blended product within the range of 10 ° C. and measuring the shear rate separately under the condition that the shear rate is 10 ° C. higher than either of the high temperature side of the flow start temperature. Absolute value of difference with viscosity is 1
It is important to perform melt molding under the condition of 000 poise or less.

When the blending amount of the olefin resin is lower than the above range, the melt moldability is not sufficiently improved. On the other hand, when the blending amount of the liquid crystal polyester is lower than the above range, gas permeation resistance, Mechanical properties, heat resistance, etc. are not sufficiently improved.

In the present invention, it has been found that the surprising fact that it is important to sufficiently mix both resins in order to effectively develop the above-mentioned multilayer distribution structure. For this purpose, the viscosities of the two resins must be relatively close and the molding conditions such as temperature should be selected accordingly. When the difference in melt viscosity between both resins exceeds the above range, the liquid crystal polyester tends to have a granular distribution, and it is difficult to develop a layered distribution structure.

In the present invention, in order to effectively develop the above-mentioned multi-layer distribution structure, it is also important that the blended product sufficiently flows during molding. For this purpose,
It is important that the blend has a melt flow rate in the above range. When the MFR is larger than the above range, the liquid crystal polyester becomes difficult to be distributed in layers. On the other hand, MFR
If the value is too small, there is a problem in terms of melt moldability.

[0029]

Preferred Embodiment of the Invention

(Liquid crystal polyester) As liquid crystal polyester resin,
Polyester derived from polycondensation of aromatic dicarboxylic acid component and aromatic diol component; Polyester obtained by polycondensation of aromatic hydroxycarboxylic acid; Copolyester of the above two polyesters; and polyester and polyethylene terephthalate And thermotropic materials such as the copolyesters mentioned above.

The proportion of divalent aromatic groups per divalent hydrocarbon group in all ester repeating units is, for example, 50% in polyethylene terephthalate, but in the range of 50 to 100% in the liquid crystal resin used in the present invention. Is desirable.

A suitable example is as follows.

Equation (1)

Embedded image A polyester composed of repeating units represented by, for example, Vectra from Celanese,

Equation (2)

Embedded image Polyester consisting of repeating units represented by, for example, Zider from Dartco,

Equation (3)

Embedded image A polyphenylhydroquinone terephthalate consisting of repeating units of

Equation (4)

Embedded image A repeating unit of PHB / PET copolymer.

Of course, the liquid crystal polyester used in the present invention is not limited to these examples. The liquid crystal resin used in the present invention should have a molecular weight sufficient to form a film, and is generally preferably one that can be thermoformed at 200 to 400 ° C. The liquid crystal polyester of "Chemical Formula 4" is particularly suitable for the purpose of the present invention.

(Olefin Resin) As the olefin resin, olefin homopolymers and copolymers used in the production of containers and other resin molded products are used. For example, low density, medium density or high density polyethylene, linear low density polyethylene, polypropylene, polybutene-1, polypentene-1, poly4-methylpentene-1, propylene-ethylene copolymer, ionomer,
Examples thereof include ethylene-acrylic copolymers and ethylene-vinyl acetate copolymers. Of course, these olefin resins can be used alone or in combination of two or more kinds.

These olefinic resins are generally used in the form of 0.
A material having an MFR of 01 to 100 g / min is preferable, and an extrusion grade or an injection grade can be appropriately selected and used according to the molding method. For the purposes of the present invention, high density polyethylene is particularly suitable as the olefinic resin. The blend containing the high-density polyethylene is particularly excellent in melt moldability and is also particularly excellent in developing a multi-layer distribution structure. The high density polyethylene preferably has a density of 0.94 to 0.97 g / cm ³ .

(Molded Structure) The multilayer distributed structure molded product according to the present invention generally comprises an olefin resin (inner and outer layers) mainly distributed in layers on the inner and outer surface sides, and a liquid crystal polyester (intermediate layer) mainly distributed in layers on the center side. ) And. The liquid crystal polyester intermediate layer is present in a substantially continuous form in the container surface direction when seen through in the thickness direction of the container wall, and the molecules are mainly uniaxially oriented. The olefin resin inner and outer layers may be substantially unoriented or oriented.

The intermediate layer being substantially continuous when seen through in the thickness direction of the container wall means that the intermediate layer is substantially continuous as shown in FIG.
(I) Film CF in which the intermediate layer ML is continuous with the inner and outer layers OL
When present in the form of, as shown in (B) of FIG.
(II) The intermediate layer ML is not in the form of a continuous film, but is in the form of a large number of flakes F, and these flakes F overlap at least at their edge portions in the thickness direction. When it appears to be continuous, and as shown in (C) of FIG. 1, (III) an intermediate state between (I) and (II) or a combination of (I) and (II). If it exists in.

The liquid crystal polyester intermediate layer in the container obtained by the present invention is characterized in that it is present in the above-mentioned shapes (I), (II), (III) and the like, and is molecularly oriented in a uniaxial direction. Since the liquid crystal polyester is molecularly oriented in a uniaxial orientation, the gas permeability resistance is improved most effectively, and particularly the oxygen permeability coefficient and the water vapor permeability coefficient are most effectively reduced.

Furthermore, in the present invention, the liquid crystal polyester layer can be uniaxially oriented by directly utilizing the flow orientation at the time of molding, does not require any special stretching orientation operation and equipment, and is gas resistant. The advantage is that significant improvements in permeability and mechanical properties are made.

In the multilayer distribution structure molded body obtained by the present invention, the liquid crystal polyester intermediate layer is present, and the oxygen permeability coefficient of the intermediate layer becomes a remarkably small value.
Gas permeation through the vessel wall of the entire container is suppressed, but excellent gas permeation resistance can be obtained even if the intermediate layer has a flaky shape as in (II) above. This is because the gas permeation passage becomes longer and the same effect as that of increasing the thickness can be obtained.

In FIG. 2 showing an example of the molded product of the present invention, this molded product 1 is a container in the shape of a tray,
It comprises a tubular or tapered body 2, a closed bottom 3 connected to the lower end of the body, and a bead or flange-shaped open end 4 provided at the upper end of the body. A lid 5 is provided separately from the container 1, and the lid 5 and the bead or flange-shaped opening end 4 are provided.
A heat seal or the like is performed between and. The liquid crystal polyester is continuously present as the intermediate layer ML over the entire body and bottom. The projection 6 located at the center of the closed bottom portion 3 corresponds to an injection type gate.

In FIG. 3 showing another example of the molded body,
The molded body 1 is in the shape of a cup or a seamless plastic can, and also comprises a tubular or tapered body 2, a closed bottom 3 and a bead or flanged open end 4. The lid 5 and the container 1 are sealed by heat sealing,
Alternatively, it is performed by tightening.

In "FIG. 4" showing still another example of the molded body, the molded body 11 is a cap, and includes a top plate portion (panel portion) 12 and a cylindrical skirt portion 13 continuous with the top plate portion (panel portion) 12. . A fine concavo-convex portion (knurled groove) 14 is provided on the outer periphery of the skirt portion for facilitating gripping of the cap, while a screw 15 for fastening and sealing with the container mouth portion is provided on the inner surface side thereof. Are formed. Top plate 1
There is a small protrusion 16 in the center of the inner surface side of 2, which corresponds to an injection type gate.

(Manufacturing Method) In the present invention, the liquid crystal polyester and the olefin resin are supplied in the form of a mixture to the hopper of the injection machine. This mixture may be a dry blend of the two or a melt blend. Dry blends include, for example, ribbon blenders, conical blenders,
Melt blending can be performed using a single-screw or twin-screw extruder, kneader, Banbury mixer, roll, or the like, while melt blending can be performed using a Henschel mixer.

In molding the blend, injection molding or extrusion molding can be used. At the time of molding, as described above, conditions should be selected such that both resins are sufficiently mixed and the blended product is sufficiently fluidized. Generally, the molding temperature of the resin is preferably 200 to 400 ° C, and particularly preferably 250 to 350 ° C.

The mixture is melt-injected into a cooled injection mold under high shear conditions. An injection machine known per se equipped with an injection plunger or a screw is used, and the mixture is injected into an injection mold through a nozzle, a sprue and a gate. As a result, the above-described distribution structure is formed in the resin flow, the liquid crystal resin is given a remarkable flow orientation, flows into the injection mold cavity, and is cooled and solidified to be the molded product of the present invention. As an injection type,
The one having a cavity corresponding to the shape of the container is used, but in order to fix the above-mentioned flow orientation to the uniaxial orientation, it is preferable to use a one-gate type injection die. The injection pressure is preferably about 100 to 2000 kg / cm ² .

In the case of extrusion molding, an extruder equipped with an arbitrary screw is preferably used as the extruder. A flat die or a ring die can be used as the die. For example, a T die method or an inflation film forming method is used for forming a film or a sheet. A ring die is used for forming tubes, pipes and parisons. By hollow molding the extruded parison,
Hollow molded containers such as bottles, tubes and tanks are molded. Further, the cup-shaped container is formed by subjecting the sheets to plug-assist molding in a molten state or solid-phase pressure molding.

[0051]

The present invention is further described by the following examples. The container materials and container properties described in Examples and Comparative Examples were evaluated and measured according to the following methods.

(A) Measurement of Melt Viscosity The shear rate and melt viscosity η (poise) were determined using a capillary polymer flow characteristic tester for molten polymer (Capirograph 1B) manufactured by Toyo Seiki Seisaku-sho, Ltd. (1) Shear stress

(3) τ = Pr / 2L (dyne / cm ² ) (2) Shear rate

[Equation 4] γ = 4Q / πR ³ (sec ^-1 ) (3) Melt viscosity

Η = τ / γ (poise = dyne · sec)
/ Cm ² ) where P: barrel internal pressure (dyne / cm ² ) R: capillary radius (cm) L: capillary length (cm) Q: volumetric outflow rate (cm ³ / sec)

(B) Injection molding machine NN75JSHhipersho manufactured by Niigata Steel Works Co., Ltd.
t7000

(C) Water vapor transmission rate test A container molded by injection molding is filled with dried silica gel in an amount of about 70% of the internal volume of the container, and after sealing, 22 ° C. and 60 ° C.
The sample was put in a tabletop constant temperature and humidity chamber set to% RH, and the change in total weight with time was measured. The amount of water vapor permeation was calculated from the amount of change.

Example 1 High-density polyethylene (HDPE) was dry-blended with liquid crystal polyester (LCP), and a mixture of 100 to 100 parts by weight of the liquid crystal polyester was mixed in an amount of 0 to 100 parts by weight by injection molding. After molding, the amount of water vapor permeation was determined and is shown in Table 1. When the cross section was observed, the liquid crystal polyester was distributed in a dense multilayer in the central part.

[0056]

[Table 1] Melt viscosity of resin used (shear rate 1 × 10 ⁴ sec ^-1 at 3
00 ° C) HDPE 2.3 × 10 ² poise LCP 3.1 × 10 ² poise LCP has a flow starting temperature of 290 ° C.

Comparative Example 1 A high-density polyethylene was dry-blended with a liquid crystal polyester different from that of Example 1, and a mixture of the liquid crystal polyester with a mixing ratio of 0 to 100 parts by weight based on 100 parts by weight was molded by injection molding. Then, the amount of water vapor permeation is calculated and shown in Table 2.
Shown in When the cross section was observed, the liquid crystal polyester was dispersed in high density polyethylene in a granular form.

[0058]

[Table 2] Melt viscosity of resin used (shear rate 1 × 10 ⁴ sec ^-1 at 3
00 ° C) HDPE 2.3 × 10 ² poise LCP 1.3 × 10 ³ poise

[0059]

According to the present invention, a blend of a liquid crystal polyester and an olefin resin, especially high density polyethylene is melt-molded under a specific condition to obtain a drawdown property or an excessive one-dimensional property during melt molding. The liquid crystal polyester and the olefin resin have a multi-layered distribution structure in the molded product by the simple operation of improving the flow tendency and molding the blended product, gas permeation resistance, heat resistance, mechanical strength, etc. It was possible to manufacture a molded structure excellent in quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a typical example of a multi-layer distribution structure in a molded structure of the present invention, where (A) is a continuous liquid crystal polyester, and (B) is a foil piece-like integrated form. (C) shows the case of these combinations.

FIG. 2 is a side sectional view of a tray-shaped container.

FIG. 3 is a cross-sectional view of a cup-shaped container.

FIG. 4 is a cross-sectional view of a resin cap.

[Explanation of symbols]

1 is a container, 2 is a body part, 3 is a closed bottom part, 4 is an open end part, 5
Is a lid, 6 is a protrusion, 7 is a container wall, 11 is a cap, 12 is a top plate portion (panel portion), 13 is a skirt portion, 14 is an uneven portion (knurled groove), 15 is a screw, 16 is a protrusion, and F is Flake, CF is a continuous film, OL is an olefin resin inner / outer surface layer, and ML is a liquid crystal polyester intermediate layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C08L 23/02 LCT C08L 23/02 LCT

Claims (5)

(57) [Claims] 1. A multi-layered distribution structure formed by melt-molding a blend containing an olefin resin and a liquid crystal polyester and having a layer containing the liquid crystal polyester preferentially and a layer containing the olefin resin preferentially. A composite resin molding structure characterized by being provided. 2. The molding structure according to claim 1, wherein the olefin resin and the liquid crystal polyester are contained in the blend in a weight ratio of 95: 5 to 5:95. 3. The molded structure according to claim 1, wherein the layer containing the olefin resin preferentially is the inner and outer surface layers and the layer containing the liquid crystal polyester preferentially is the intermediate layer. 4. The molded structure according to claim 1, wherein the olefin resin is high density polyethylene. 5. The shear rate between the olefin resin and the liquid crystal polyester is 10 relative to the high temperature side of either of the flow initiation temperatures.
Multilayer distribution characterized by being melt-molded under the condition that the absolute value of the difference between the melt viscosity of the olefin resin and the melt viscosity of the liquid crystal polyester is 1000 poise or less when measured separately under conditions of a high temperature of ℃. Manufacturing method of composite resin molding structure of structure.