JP2000318001A - Resin molding method and production of molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amt. of a low b.p. volatile component contained in a molded article even if a resin, especially, a thermoplastic polyester resin is supplied in a state much or little in moisture content at the time of molding in a resin plasticizing and molding method and a molded article producing method. SOLUTION: In a resin molding method using a molding screw type plasticizing apparatus having a cylinder and a screw, a first vent is provided at the position on the cylinder immediately after a resin is melted and plasticized and a second vent is provided at the position on the cylinder on the downstream side of the first vent and the first and second vents are held to a vacuum state to mold a molded article.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for molding a resin.

[0002]

2. Description of the Related Art Thermoplastic polyester resins are injection-molded because of their excellent physical properties, moldability and cost performance.
Widely used for extrusion molding, blow molding, film, etc. In particular, polyethylene terephthalate and polyethylene naphthalate are widely used for food packaging because of their excellent transparency and heat resistance.

However, since these have an ester bond in the molecular chain, when heated and melted in the presence of moisture, the molecular weight is remarkably reduced, and problems in quality such as physical properties are likely to occur.

When used for food packaging, electronic materials, etc., low-boiling volatile gas components and the like generated during the heat plasticization process lower the quality of the product, so that low-boiling volatile gas components and the like are suppressed. There is a need.

[0005] Therefore, an opening (hereinafter sometimes referred to as a vent) is provided in a cylinder of a screw-type plasticizing apparatus,
Further, it is widely and generally practiced to provide a mechanism (hereinafter, sometimes referred to as a vent mechanism) for positively removing moisture or volatile components by reducing the pressure of the vent. Actually, many examples in which the vent mechanism is applied to a plasticizing apparatus for injection molding are known, for example, disclosed in Japanese Patent Application Laid-Open No. 58-38135. In such a conventional method, since there is only one vent, it is difficult to remove both moisture and volatile components at a satisfactory level.

On the other hand, it is known to provide two vents in order to enhance the effect of removal from the vents.
No. 54-119554.

[0007]

However, when this method is applied to a resin, particularly a thermoplastic polyester resin, there is a problem that the thermoplastic polyester resin is hydrolyzed and thermally decomposed, and a satisfactory effect cannot be obtained.

It is an object of the present invention to provide a resin, particularly a thermoplastic polyester resin, which is supplied at a high or low moisture content at the time of molding, and which has a low boiling point volatile component contained in a molded article. It is an object of the present invention to provide a method for plasticizing and molding a resin, particularly a thermoplastic polyester resin, and a method for producing a molded article, which can reduce the amount.

Further, since the low-boiling volatile components are derived from moisture introduced together with the raw materials at the initial stage of plasticization and components generated by thermal decomposition at the final stage of plasticization, another object of the present invention is to provide a method for hydrolyzing a resin. It is an object of the present invention to provide a method for plasticizing and molding a resin, particularly a thermoplastic polyester resin, and a method for producing a molded article, in which moisture is removed from a vent before generation, and other volatile components are removed later.

[0010]

Means for Solving the Problems: The present invention relates to: 1) A method for molding a resin using a molding screw-type plasticizing apparatus having a cylinder and a screw, the method comprising the steps of: A first vent is provided, a second vent is provided at a position on the cylinder downstream of the first vent, and the first vent and the second vent are maintained in a reduced pressure state to form a molded product. Item 2) In a method for molding a thermoplastic polyester resin using a single-screw type plasticizing apparatus for molding having a cylinder and a screw, a method is provided in which a position between a compression end portion and a position satisfying the following expression is satisfied. A first vent is provided at a position on the cylinder, and further, at a position on the cylinder between a position 2D upstream from the position of the screw tip and a position 5D upstream from the position of the screw tip. A single-screw plasticizing apparatus for molding, in which two vents are provided and the first vent and the second vent are maintained in a reduced pressure state, is operated under conditions satisfying all of the following expressions to form a molded product. To mold a thermoplastic polyester resin,

[0011]

## EQU00003 ## Position of the first vent: T (L3) <15 seconds Average residence time of the screw 1D: T (L1) = RT / L1 Residence time from the position of the hopper to the position of the end of compression: T (L2) = L2 × T (L1) Residence time from the position of the end of compression to the position of the first vent: T (L3) = L3 × T (L1) D: Screw diameter L1: From the position of the hopper to the position of the first vent L2: distance from the hopper position to the position of the end of compression L3: distance from the position of the end of compression to the position of the first vent RT: actual measurement of the resin residence time from the position of the hopper to the position of the first vent Value (However, 1D means the distance of 1 time of D, 2D means the distance of 2 times of D, and 5D means the distance of 5 times of D. The position of the compression end part and the position of the screw tip are At the most downstream position of the movable range in the cylinder. In the method for molding a thermoplastic polyester resin using a twin-screw type plasticizing device for molding having a cylinder and a screw, the melting is terminated. A first vent is provided at a position on the cylinder between the position of the part and a position satisfying the following expression, and further, a position between a position 2D upstream from the position of the screw tip and a position 5D upstream from the position of the screw tip. A second screw is provided at a position on the cylinder, and the twin-screw plasticizing device for molding, in which the first vent and the second vent are maintained in a reduced pressure state, is operated under the conditions satisfying all of the following expressions to produce a molded product. A method for molding a thermoplastic polyester resin, characterized by molding.

[0012]

## EQU00004 ## Position of the first vent: T (L3) <15 seconds Average residence time of the screw 1D: T (L1) = RT / L1 Residence time from the position of the hopper to the position of the melting end portion: T (L2) = L2 × T (L1) Residence time from the position of the end of melting to the position of the first vent: T (L3) = L3 × T (L1) D: Screw diameter L1: From the position of the hopper to the position of the first vent L2: Distance from hopper position to compression end position L3: Distance from melting end position to first vent position RT: Actual measurement of resin residence time from hopper position to first vent position Value (However, 1D means the distance of 1 time of D, 2D means the distance of 2 times of D, and 5D means the distance of 5 times of D. The position of the melting end part and the position of the screw tip are At the most downstream position of the movable range in the cylinder. When a position of the position and the screw tip of each end of melting unit.) The present invention will be described below in detail.

[Resin] As the resin, a thermoplastic resin and a composition thereof are used. As the resin, a thermoplastic polyester resin is preferable.

The thermoplastic polyester resin includes known thermoplastic polyesters and their compositions. From the viewpoints of transparency, mechanical properties and hygiene, polyethylene terephthalate and polyethylene naphthalenedicarboxylate are preferred. When these are used, a food packaging container excellent in transparency, mechanical properties, and hygiene can be manufactured.

Polyethylene naphthalenedicarboxylate is a polyester comprising a dicarboxylic acid component having a naphthalenedicarboxylic acid component as a main component and a diol component having an ethylene glycol component as a main component.
The main component means preferably 50 mol% or more, more preferably 80 mol% of the total dicarboxylic acid component in the case of the dicarboxylic acid component, and preferably 50 mol% of the total diol component in the case of the diol component. As mentioned above, more preferably, it refers to 80 mol%.

As long as the components constituting the thermoplastic polyester satisfy this condition, a copolymerized component may be used, or a component blended with another kind of resin may be used.

That is, the thermoplastic polyester permits the copolymerization of up to 50 mol% of the total dicarboxylic acid component and the copolymerization of up to 50 mol% of the total diol component. It allows blending with various resins in a range where the ethylene naphthalenedicarboxylate units are at least 50% by weight of the total resin component. As the thermoplastic polyester, polyethylene-2,6-naphthalenedicarboxylate is particularly preferred.

[Screw-type plasticizing device] A screw-type plasticizing device is used as a forming-type screw plasticizing device. This is a device in which a resin material is transported in a barrel (heating cylinder) by a screw installed in the barrel, and is melted by receiving heat from the barrel at this time.

As the screw type plasticizing device, for example, a single screw type plasticizing device and a twin screw type plasticizing device can be used.

When a single-screw plasticizing device is used, the screw configuration can be divided into a supply section, a compression section, and a measurement section. Different pressure. The most downstream portion of the compression section is referred to as a compression end section.

When a twin-screw plasticizing device is used, the screw configuration can be divided into a supply section, a melting section, and a measuring section. And the resin pressure inside the screw is different. The most downstream part of the fusion part is referred to as a fusion end part.

In the present invention, the position of the end of compression when the single-screw plasticizing device is used is the same as the position of the end of melting when the twin-screw plasticizing device is used. Therefore, the term “compression end” may be used in place of the term “melt end”, but these are synonymous.

[Vent] In the screw-type plasticizing apparatus for molding, a first vent is provided at a position on the cylinder immediately after the resin is melt-plasticized, and a second vent is provided at a position on the cylinder downstream of the first vent. Provide a vent.

When a single-screw screw plasticizing device for molding is used as the screw-type plasticizing device for molding, the first screw is placed at a position on the cylinder between the position of the end of compression and a position satisfying the following expression. A vent is provided and 2
It is preferable to provide the second vent at a position on the cylinder between the position upstream of D and the position 5D upstream from the position of the screw tip.

[0025]

## EQU00005 ## Position of the first vent: T (L3) <15 seconds Average residence time of the screw 1D: T (L1) = RT / L1 Residence time from the position of the hopper to the position of the compression end portion: T (L2) = L2 × T (L1) Residence time from the compression end position to the first vent position: T (L3) = L3 × T (L1) D: Screw diameter L1: From hopper position to first vent position L2: distance from the hopper position to the position of the end of compression L3: distance from the position of the end of compression to the position of the first vent RT: actual measurement of the resin residence time from the position of the hopper to the position of the first vent Value (However, 1D means the distance of 1 time of D, 2D means the distance of 2 times of D, and 5D means the distance of 5 times of D. The position of the compression end part and the position of the screw tip are At the most downstream position of the movable range in the cylinder. At the time of the first vent position, when T (L3) is less than 15 seconds, the moisture contained in the molten thermoplastic polyester resin is: The resin is quickly removed before being consumed in the hydrolysis reaction of the resin, and a molded article can be formed without substantially causing thermal degradation such as hydrolysis. Therefore, it is preferable to set T (L3) to less than 15 seconds by setting the position of the first vent and setting the operating conditions. First
By disposing the vent at the above position, water can be removed at an early stage when the thermoplastic polyester resin is melted, and hydrolysis of the thermoplastic polyester resin can be prevented.

By installing the second vent at the above-mentioned position, the resin temperature and the resin pressure are adjusted through the measuring section, the unmelted material disappears, and the resin state is adjusted. It is possible to effectively remove the volatile components having a low boiling point. As a result, a molded article having a small content of volatile components can be formed without substantially thermally deteriorating the thermoplastic polyester resin. In this respect, the position of the second vent is particularly preferably between a position 2D upstream from the screw tip and a position 3D upstream from the screw tip.

On the other hand, if the second vent is installed further upstream from the above position, that is, on the hopper side, volatile components generated in the screw zone downstream of the second vent cannot be removed, and volatile components in the molded article cannot be removed. The concentration increases. Second
If the vent is installed downstream from the above position, that is, on the nozzle side, there is a possibility that the vent will rise during molding.

The first vent and the second vent are maintained at a reduced pressure. The first vent is preferably 80 torr
The pressure is kept at a reduced pressure of 10 torr or less, particularly preferably 1 torr or less. The second vent is maintained at a reduced pressure of preferably 80 torr or less, more preferably 10 torr or less, and particularly preferably 1 torr or less. Unless the first vent and the second vent are maintained in a reduced pressure state, the effects of the present invention cannot be exhibited. In order to maintain such reduced pressure, a rotary vacuum pump can be generally used.

A kneading section and a measuring section can be provided downstream of the position of the first vent. In the measuring section, a short kneading section may be provided for the purpose of finally making the resin temperature uniform.

In the present invention, a vent-up prevention mechanism may be provided, such as closing the vent when the screw stops after the measurement.

The present invention can be applied to a plasticizing device for injection molding, and can be preferably applied to a screw-type plasticizing device of an in-line type injection molding machine. In that case,
In the in-line type, since the screw moves, it is necessary to provide the length of the vent portion more than the screw movement amount.

The present invention can be applied to a pre-plastic injection molding machine. In this case, since the screw does not move in the measuring process as compared with the in-line type injection molding machine, the degree of freedom in designing the vent increases, and a favorable result can be obtained.

[0033]

The present invention will be described in more detail with reference to the following examples.

The cylinder temperature of the plasticizer is 290 ° C. in each case.

The following were used as the thermoplastic polyester.

The characteristics are measured by the following method.

(1) Thermoplastic polyester resin The following were used as the thermoplastic polyester resin.

After a transesterification reaction of dimethyl-2,6-naphthalenedicarboxylate and ethylene glycol with a manganese acetate catalyst according to a conventional method, phosphoric acid was added to stop the reaction, and then germanium dioxide was added to cause a melt polymerization reaction. To obtain polyethylene-2,6-naphthalenedicarboxylate (hereinafter abbreviated as PEN).

The obtained PEN is composed of 100 mol% of a 2,6-naphthalenedicarboxylic acid component and 100 mol% of an ethylene glycol component, and has an intrinsic viscosity of 0. 0 measured at 25 ° C. in an orthochlorofinol solvent. 55, and the moisture content in a non-dried state was 0.12% by weight. In the case of extruding and molding a thermoplastic polyester resin, usually, a drying treatment is indispensable, and a desirable moisture content is 100 ppm or less.

(2) Viscosity retention The intrinsic viscosity of PEN before plasticization and the P of the molded article
The limiting viscosity number of EN was calculated by measuring in 35 ° C. orthochlorophenol solvent. The viscosity retention is represented by the following equation.

Viscosity retention = (PEN intrinsic viscosity number of molded article) / (PEN intrinsic viscosity number before plasticization) (3) Volatile Content The molded article was pulverized into a sample. Then, the amount of acetaldehyde (hereinafter, referred to as AA amount) released from 3 g of the sample when heated at 150 ° C. for 1 hour was quantitatively analyzed by a headspace gas chromatograph.

(4) Moisture Retention Measurement The moisture content was measured using a Karl Fischer moisture meter.

(5) Residence time from the hopper to the first vent (RT) The time until the colored chips were charged from the hopper and passed below the vent was measured visually.

Example 1 The above PEN was used as a thermoplastic polyester resin in an undried state.

As a plasticizer, a single shaft 4 having an L / D of 24
A 0 mm extruder was used.

The screw is composed of a supply section, a compression section, and a measurement section. The supply section is connected to the compression section, and the compression section is connected to the measurement section.

The thermoplastic polyester resin proceeds from the supply section to the compression section and melts at the position of the compression end section. The thermoplastic polyester resin in the molten state passes through a full-flight feed portion between a position 1D downstream from the position of the compression end portion and a position 3D downstream from the position of the compression end portion. It reaches the vent part set at the position 3D downstream from the position. The vent portion has a screw groove depth greater than the feed portion after the compression portion. Figure 3 shows the screw configuration
Shown in

A first vent was installed at a position 3D downstream from the position of the compression end portion, and a second vent was installed at a position 5D upstream from the tip of the screw. These vents are 10 ^-1 to
It degassed so that it might be in rr decompression state.

Discharge rate 12 kg / h, screw speed 12
The residence time T (L3) from the end of compression to the first vent when operating at 0 rpm was estimated to be 8.2 seconds.

Table 1 shows the results. The decrease in molecular weight was small and the amount of acetaldehyde as a volatile component was also small.

Example 2 The above PEN was used as a thermoplastic polyester resin in an undried state.

As a plasticizing apparatus, a coaxial twin screw 30 mm extruder having an L / D of 40 was used.

The screw configuration includes a supply section, a melting section, and a measuring section. The supply section is connected to the compression section, and the compression section is connected to the measurement section. This is a rapid compression that becomes a melting end portion in 3D from the melting start portion. FIG. 4 shows a screw configuration diagram.
This screw configuration is almost the same as that of the single-screw screw of the first embodiment. However, since the plasticizing device was a twin-screw plasticizing device, the melting portion formed of a kneading disk was used instead of the compression portion of the single-screw screw. In the barrel where the vent is installed,
Using kneading to prevent vent up,
The vent seal effect was developed.

A first vent was set at a position 2D downstream from the end of the melting part. Then, a second vent was set at a position 3D upstream from the screw tip. These vents
It degassed so that it might become a pressure-reduced state of 0 ^-1 torr.

Discharge rate 20 kg / h, screw rotation speed 80
The residence time T (L3) from the end of melting to the first vent when operating at rpm was estimated to be 4.6 seconds.

Table 1 shows the results.

The decrease in molecular weight was small, and the amount of acetaldehyde as a volatile component was also small. As described above, the same effects as those of the single screw can be obtained with the twin screw.

[0058]

[Table 1]

Comparative Example 1 The above PEN was used as a thermoplastic polyester resin in an undried state.

As a plasticizing device, a single shaft 4 having an L / D of 24
A 0 mm extruder was used. The screw includes a supply section, a compression section, and a measurement section. The supply section is connected to the compression section, and the compression section is connected to the measurement section. The compression is rapid compression, which becomes the compression end part 3D downstream from the compression start part, but then becomes a full flight. This screw configuration is shown in FIG. No vent is provided.

Table 1 shows the results. The molecular weight was remarkably reduced and acetaldehyde was generated frequently.

In this case, due to the hydrolysis, the molecular weight of the thermoplastic polyester was reduced, the mechanical properties were reduced, and the volatile component remained in the molded article at a high concentration.

Comparative Example 2 The above PEN was used as a thermoplastic polyester resin in an undried state.

As a plasticizing device, a single shaft 4 having an L / D of 24
A 0 mm extruder was used. The screw has a configuration in which a vent is provided in a part of the measuring section. The position of the vent is a portion where the groove depth of the full flight is increased. FIG. 2 shows the screw configuration. This is a configuration in which rapid compression is performed at a compression end portion 3D downstream from the compression start portion, and thereafter a full flight is performed.

One vent was installed, and it was installed at a position 3D upstream from the tip of the screw. The vent was evacuated to a reduced pressure of 10 ^-1 torr.

Discharge rate 20 kg / h, screw rotation speed 80
The residence time T (L3) from the fusion zone to the vent when operating at rpm was estimated to be 38 seconds.

Table 1 shows the results.

In this case, the molecular weight was significantly reduced. It is considered that moisture contained in the thermoplastic polyester pellets remained, and the moisture was consumed by hydrolysis of the thermoplastic polyester, causing a decrease in molecular weight.

Comparative Example 3 The above-mentioned PEN was used in a wet state as a thermoplastic polyester resin.

As a plasticizing apparatus, a coaxial twin screw 30 mm extruder having an L / D of 40 was used. The screw is composed of a supply section, a melting section (kneading disk), and a measuring section. The supplying section follows the melting section, and the melting section follows the measuring section. Fig. 5 shows the screw configuration.

One vent was installed, and 28 minutes from the end of melting.
D Installed downstream. The vent was evacuated to a reduced pressure of 10 ^-1 torr.

Discharge rate 12 kg / h, screw rotation speed 12
The residence time T (L3) from the fusion zone to the vent when operating at 0 rpm was estimated to be 59 seconds.

Table 1 shows the results.

The molecular weight was reduced, and acetaldehyde as a volatile component remained at a high concentration.

[0075]

According to the present invention, it is possible to remove water introduced together with the resin raw material at the beginning of plasticization and low-boiling volatile components generated by thermal decomposition at the end of plasticization. As a result, even when the raw material has a high moisture content, a molded article having a low volatile component content can be stably manufactured.

That is, according to the present invention, when the resin, particularly the thermoplastic polyester resin, is supplied with a high or low moisture content at the time of molding, the low boiling point contained in the molded article can be obtained. It is possible to provide a method for plasticizing and molding a resin, particularly a thermoplastic polyester resin, and a method for producing a molded article, which can reduce the amount of volatile components.

[Brief description of the drawings]

FIG. 1 is a diagram of Comparative Example 1. It is a normal single screw of D = 40 mm.

FIG. 2 is a diagram of Comparative Example 2. This is a normal vent type single screw. A vent was provided in a part of the measuring section.

FIG. 3 is a diagram of the first embodiment.

FIG. 4 is a diagram of a second embodiment. This is an example in which the present invention is applied to a twin-screw plasticizing apparatus for molding. A first vent and a second vent are provided.

FIG. 5 is a diagram of Comparative Example 3. It is an example of a twin-screw plasticizing device for molding.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4F071 AA45 BB05 BC07 4F201 AA04 AA24 AA26 BA06 BN18 BN39 BQ07 BQ18 4F206 AA04 AA24 AA26 JA07 JD02 JD03 JD05 JL02 JQ03 JQ04 4J029 AA03 AB07 AC01 BA01

Claims (7)

[Claims] In a method of molding a resin using a molding screw-type plasticizing apparatus having a cylinder and a screw, a first vent is provided at a position on the cylinder immediately after the resin is melt-plasticized. A method of molding a resin, comprising: providing a second vent at a position on a downstream cylinder; maintaining the first vent and the second vent in a reduced pressure state; and molding a molded product. 2. A method for molding a thermoplastic polyester resin using a single screw type plasticizing apparatus for molding having a cylinder and a screw, wherein a position on a cylinder between a position of a compression end portion and a position satisfying the following expression. And a second vent at a position on the cylinder between a position 2D upstream from the position of the screw tip and a position 5D upstream from the position of the screw tip, and the first vent and the second vent are provided.
A method for molding a thermoplastic polyester resin, comprising: operating a molding single-screw plasticizing apparatus in which a vent is maintained in a reduced pressure state, and operating under conditions satisfying all of the following expressions to mold a molded article. ## EQU00001 ## Position of the first vent: T (L3) <15 seconds Average residence time of the screw 1D: T (L1) = RT / L1 Residence time from the position of the hopper to the position of the end of compression: T (L2) = L2 × T (L1) Residence time from the compression end position to the first vent position: T (L3) = L3 × T (L1) D: Screw diameter L1: From hopper position to first vent position L2: distance from the hopper position to the position of the end of compression L3: distance from the position of the end of compression to the position of the first vent RT: actual measurement of the resin residence time from the position of the hopper to the position of the first vent Value (However, 1D means the distance of 1 time of D, 2D means the distance of 2 times of D, and 5D means the distance of 5 times of D. The position of the compression end part and the position of the screw tip are At the most downstream position of the movable range in the cylinder. When a position of the position and the screw tip of each compression termination unit.) 3. A method for molding a thermoplastic polyester resin using a twin-screw plasticizing apparatus for molding having a cylinder and a screw, wherein a position on a cylinder between a position of a melting end portion and a position satisfying the following expression. And a second vent at a position on the cylinder between a position 2D upstream from the position of the screw tip and a position 5D upstream from the position of the screw tip, and the first vent and the second vent are provided.
A method for molding a thermoplastic polyester resin, comprising operating a biaxial screw-type plasticizing apparatus for molding with a vent maintained in a reduced pressure state under conditions satisfying all of the following expressions to mold a molded article. ## EQU00002 ## Position of the first vent: T (L3) <15 seconds Average residence time of the screw 1D: T (L1) = RT / L1 Residence time from the position of the hopper to the position of the melting end: T (L2) = L2 × T (L1) Residence time from the position of the end of melting to the position of the first vent: T (L3) = L3 × T (L1) D: Screw diameter L1: From the position of the hopper to the position of the first vent L2: Distance from hopper position to compression end position L3: Distance from melting end position to first vent position RT: Actual measurement of resin residence time from hopper position to first vent position Value (However, 1D means the distance of 1 time of D, 2D means the distance of 2 times of D, and 5D means the distance of 5 times of D. The position of the melting end part and the position of the screw tip are At the most downstream position of the movable range in the cylinder. When a position of the position and the screw tip of each end of melting unit.) 4. The thermoplastic polyester resin is polyethylene-2,6-naphthalenedicarboxylate.
The molding method according to claim 2. 5. A first vent and a second vent by a deaerator.
The molding method according to claim 2 or 3, wherein the vent is maintained at a reduced pressure. 6. The molding method according to claim 1, wherein the screw-type plasticizing device for molding is a plasticizing device for injection molding. 7. A method for producing a molded article using the molding method according to claim 1.