JPH03247627A - Molding of polymer containing methacrylimide - Google Patents

Abstract

PURPOSE:To obtain a polymer having excellent color tone and capable of giving a molded article free from yellowness even from a polymer left standing over a long period by molding a polymer after decreasing the oxygen concentration in the polymer below the equilibrium concentration under a specific oxygen partial pressure in the atmosphere. CONSTITUTION:A methacrylimide-containing polymer composed of 2-100wt.% of a structural unit of formula (R is H or 1-20C aliphatic, aromatic or alicyclic hydrocarbon group) and 0-98wt.% of a structural unit derived from ethylenic monomer is molded under heating while suppressing the oxygen concentration in the polymer below the equilibrium concentration under the atmospheric oxygen partial pressure of 60mmHg. Preferably, the polymer is molded after storing in an inert gas atmosphere having an oxygen partial pressure of <=60mmHg.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for molding a methacrylimide-containing polymer with excellent color tone.

[Conventional technology]

Methacrylimide-containing polymers have excellent heat resistance, weather resistance, and mechanical properties as well as transparency, so they are used in lamp lenses,
Lighting covers are rapidly being used for applications such as light guide plates and interior and exterior parts for vehicles.

It is known that methacrylic imide-containing polymers can be obtained by reacting methacrylic polymers with primary amines or ammonia. A method has been proposed in which a methacrylimide-containing polymer having excellent heat resistance and transparency is obtained by reacting a g-grade amine such as methylamine and a g-grade amine such as methylamine at high temperature and then removing volatile components.

[Problem to be solved by the invention]

However, although the transparency and color tone of the methacrylimide-containing polymer obtained by the above method are certainly excellent, the color tone after production is lower than that of a molded article that is heat-shaped immediately after the polymer is created. After 1,000 days, the color tone of the heat-formed molded product becomes slightly yellow.

[Means to solve the problem]

Therefore, the present inventors have solved the problem that the color tone of a methacrylimide-containing polymer left in a Kandai-kabuto for a long period of time after manufacture, or a molded product obtained by drying the polymer with hot air and heating it, has a slightly high degree of yellow. As a result of intensive studies to solve this problem, we found that the color tone of the molded product that is obtained depends on the oxygen concentration in the material used for molding, and that by reducing the oxygen concentration in the material, molded products with good color tone can be obtained. I found out what I can get.

For example, the oxygen concentration in the methacrylimide-containing polymer obtained by the above method is so small that it can be considered as virtually zero immediately after production, and even when molded, the yellowness of the molded product is small; Alternatively, by leaving it in a moisture-proof atmosphere, it gradually absorbs oxygen from the atmosphere, and when it is dried in the trench or with hot air and subjected to molding, a molded product with a strong yellowish tinge can be obtained. Since no change in color tone of the molded product was observed even after being left for a long period of time after molding, it is clear that yellowing occurred during hot molding.

The present invention has been made in view of these points, and its gist is expressed by the following general formula (1) (wherein R is H, an aliphatic group having 1 to 20 carbon atoms, or an aromatic compound. 4 L<'
represents alicyclic hydrogen chloride. ) Structural unit 2~
When thermoforming a methacrylimide-containing polymer consisting of 100% by weight and a structural unit O to 98% by weight derived from an ethylenic monomer, the oxygen concentration in the polymer is set to below the equilibrium concentration at an atmospheric oxygen partial pressure of 60mHH. A method for molding a methacrylimide-containing polymer, characterized by subjecting it to molding.

The methacrylimide-containing polymer that is the object of the present invention has a structure represented by the above general formula (1), that is, it is composed of a methacrylimide unit and a structural unit derived from an ethylenic monomer. Ethylene monomers such as methacrylic acid, methacrylic esters, mixtures thereof, acrylic esters copolymerizable with these, styrene, α-methylstyrene, and other monoethylenic monomers, methacrylic esters Examples of esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, and examples of acrylic esters include acrylic acid. Methyl, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, acrylic f112-
Examples include ethylhexyl and benzyl acrylate.

Furthermore, as units other than methacrylimide units, units in which some of these ethylenic monomer units become amide units during imidization reaction are also included.

Further, in the present invention, the effects of the present invention can be obtained as long as the methacrylimide-containing polymer contains 2 weight or more of methacrylimide units represented by the general formula (I), but 10! When the amount of i is 4 or more, the effect of the present invention becomes greater, and when the amount of i is 4 or more, the effect of the present invention becomes remarkable.

In method 2 of the present invention, the oxygen concentration in the methacrylimide-containing 1 coalescence, which is the molding material, is adjusted to 60 mH at the atmospheric oxygen partial pressure.
It is necessary to use it for molding at a concentration lower than the equilibrium concentration in g. More preferably, the atmospheric oxygen partial pressure is 20 mHg.
In this case, the color wI4 of the molded product becomes stable to such an extent that almost no change is observed.

A method for keeping the oxygen concentration in the material before molding within the above range is to store the methacrylimide-containing polymer, which is the molding material, in an inert gas atmosphere, under a pressure of 300 mw.
A method of sealing storage in a reduced pressure atmosphere of Hg or less and a method of drying the material under reduced pressure by heating immediately before molding are suitable.

When storing the material in an inert gas atmosphere, any type of inert gas may be used as long as it does not deteriorate the material during heat forming, but from the viewpoint of cost and ease of handling, nitrogen or carbon oxide, Or a mixture thereof is preferred.

Further, the purity of the inert gas is better as it is thinner, but in order to achieve the purpose of lowering the oxygen partial pressure, it is preferably at least 9 parts or more, more preferably 97 parts or more.

When storing materials in a vacuum atmosphere, the pressure should be increased to 50%.
It is preferable to set it to 0 mHg or less.

More preferably, it is 100 mHg or less, but the oxygen partial pressure can be further reduced by using an inert gas in combination.

When drying the material under reduced pressure by heating immediately before molding, the temperature need not exceed the heat distortion temperature of the material, but in order to reduce the oxygen concentration in a short time, it is necessary to
It is efficient to carry out the process at a temperature as low as ℃. Furthermore, if the material absorbs moisture, it is efficient to carry out the step between the heat deformation temperature and a temperature 30° C. lower than the heat deformation temperature.

Also, the lower the pressure, the more efficient deoxidation is,
At least 500 mHg or less, preferably Fi100m
A good color tone will be obtained if the temperature is below mHg.

By subjecting the methacrylimide-containing polymer whose oxygen concentration has been reduced as described above to heat-melt molding, changes in color tone due to the length of storage period are significantly reduced, and molded products with less yellowish tinge can be stably obtained. be able to.

The effects of the present invention can be obtained by any molding method as long as it is hot melt molding, and specific examples include injection molding, press molding, extrusion molding, and blow molding. A material with a reduced oxygen concentration starts absorbing oxygen as soon as it is taken out into the atmosphere, so the shorter the period of time it is left until molding, the better. 2
It is preferable to keep it within 1 day, more preferably 1 day.
I'll be back within 2 hours. Furthermore, the effects of the present invention will be even more pronounced if the inside of the hopper of the molding machine is made into an inert gas atmosphere for the purpose of shortening the contact time between the material and the atmosphere and preventing the air from being drawn in during molding.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, physical property evaluation in Examples was performed by the following method.

(1) Imidization (glutarimide unit content) The nitrogen content of the polymer was determined by elemental analysis, and the weight ratio was determined by calculating the ratio of the weight of the glutarimide ring unit to the total weight of the polymer.

Total light transmittance It was measured using a MU STM D-1003.

(3) Yellowness Index (YI[) It was measured using a color difference meter color analyzer.

Production Example 1 70 parts of methyl methacrylate, 24 parts of toluene, 6 parts of methanol, to 1.1'-azobiscyclo (2) 08 parts of xanecarbonitrile α, 325 parts of 2.2-azobisisobutyronitrile CL0, n-octylmercaptan ( After reducing the amount of dissolved oxygen in the raw material feed liquid consisting of 115 parts to less than 1 pprn, it was passed through a filter for removing microparticles to a first stirred tank reactor with an internal volume of 20 L at a temperature of 110°C at a rate of 3 kg/Hr. The polymerization conversion rate was measured immediately after leaving the reactor and was found to be 575t6.

This polymerization solution was introduced into a second multi-tubular heat exchange type reactor (consisting of 30 straight tubes with an inner diameter of 12.7 cm and a length of 1000 + W), and polymerization was carried out at a temperature of 125°C for 95 minutes. Polymerization was allowed to proceed until the conversion rate was reached. Furthermore, this polymerization liquid was mixed with the following imidized substance and supplied to the stirred tank type reactor in the third reaction zone.

On the other hand, dissolve the imidized substance (methylamine) in percent bf.
After reducing the amount of dissolved oxygen to less than 1 ppm in the same way as in the raw material feed liquid treatment, methylamine was added to the mixture (toluene: methanol - 1:1 weight ratio) to reduce the amount of dissolved oxygen to less than 1 ppm. The mixture was supplied at a rate of 1 hr, mixed with the above polymerization solution, and supplied to the third reaction zone. The imidized substance and the polymerization solution were mixed at 100° C. for 5 minutes, and after thorough mixing using an in-line mixer, the mixture was supplied to the third reaction zone. The mixed liquid of the polymerization liquid and the imidization substance is in the third reaction zone (inner volume: 15 L, temperature: 235°C).
After the imidization reaction is carried out by supplying the reaction solution from the lower part of the stirred reactor, the reaction solution that leaves this reaction zone is supplied to the stirred tank reactor in the upper part, which is a 3L aging reaction zone at a temperature of 235°C. did.

The reaction liquid exiting these reaction zones is flushed from the nozzle port into a tank regulated under a reduced pressure of 100 torr.
The flashed polymer is supplied onto a screw (the shaft is made of ultra-hard steel) which has been made corrosion resistant by chrome plating,
The material was shaped into a strand using a 30φ double-bent twin-screw extrusion rod holding a stainless steel barrel, and made into a pellet.

The extruder with a double vent had a vent part vacuum level of 5, Hg 1 temperature of 260°C, a metal ring part temperature of 270°C, and a die part temperature of 255°C. When the infrared spectrum of the obtained pellet-like polymer was measured, the wave number was 1720 ex-'%.
Absorption characteristic of methacrylimide was observed at 750 yt-'', and it was confirmed that the polymer was a methacrylimide-containing polymer.

Further, the imidization rate of the polymer determined by nitrogen elemental analysis was 804.

This methacrylimide-containing polymer is designated as sample G-1.

Production Example 2 A methacrylimide-containing polymer (sample G-2) with an imidization rate of 90 was obtained in the same manner as Production Example 1 except that the amount of methylamine solution supplied was 1.2 kg/Hr.

Reference Example 1 Immediately after sample G-1 was obtained in Production Example 1, injection molding was performed (cylinder temperature: 300°C), and the total light transmittance of the obtained molded specimen was 92, and the YI value was 10. Met. The molded specimen was then left in the air for 30 days and measured again, and the total light transmittance was 92% and the YI value was 1.
It was 0.

Example 1 Immediately after obtaining Sample G-1 in Production Example 1, the pellet was sealed and packaged. A nitrogen atmosphere was created inside the package, and the oxygen concentration in the atmosphere measured with an oxygen concentration meter was less than 2 pm. The product was stored in a sealed package for 7 days, and injection molding was performed in the same manner as in Reference Example 1.

The evaluation results are shown in Table-1.

Example 2 An experiment was conducted in the same manner as in Example 1 except that the storage period was 30 days. The results are shown in Table-1.

Example 3 An experiment was conducted in the same manner as in Example 1 except that the atmosphere inside the package was carbon dioxide. The results are shown in Table-1.

Comparative Example 1 Sample G-1 was stored in an unsealed package under atmospheric conditions for 7 days, and injection molded in the same manner as in Reference Example 1. The results are shown in Table-1.

Example 4 After storing Sample G-1 in an unsealed package under atmospheric conditions for 30 days, injection molding was performed in the same manner as in Reference Example 1 immediately after applying vacuum pressure (pressure 20 mHg) for 130" C11 $ hours. The results are shown in Table 1.

Comparative Example 2 An experiment was conducted in the same manner as in Example 4 except that hot air drying was performed at 130''C for 16 hours instead of vacuum drying.

The results are shown in Table-1.

Comparative Example 3 Sample G-1 was sealed and packaged in the air and stored in a moisture-proof manner for 7 days, and then injection molded in the same manner as in Reference Example 1. The results are shown in Table-1.

Comparative Example 4 An experiment was conducted in the same manner as Comparative Example 13 except that the moisture-proof storage period was 30 days. The results are shown in Table-1.

Example 5 Sample G-1 was placed in a vacuum sealed container (pressure: approximately 1somHg) K7
After being stored for several days, injection molding was performed in the same manner as in Reference Example 1. The results are shown in Table-1.

Example 6 An experiment was conducted in the same manner as in Example 5 except that the pressure inside the vacuum sealed container was set to 20 wag. The results are shown in Table-1.

Reference Example 2 Immediately after sample G-1 was obtained in Production Example 2, injection molding (V
When the molded specimen obtained had a total light transmittance of 924 and a Y/I of 1.0. The molded specimen was then left in the air for 30 days and measured again. The results are shown in Table-1.

Examples 7 to 12 Using sample G-2, experiments were conducted in the same manner as in Examples 1 to 5, respectively. The results are shown in Table-1.

Comparative Examples 5 to 8 Using sample G-2, experiments were conducted in the same manner as in Comparative Examples 1 to 4, respectively. The results are shown in Table-1.

Example 13 Except for closing the phonetic atmosphere inside the hopper of the injection molding machine. Example 8 The experiment was conducted in the same way.

Conclusion show the fruit Shown below.

Table 1 (lIe) ['Effects of the Invention] According to the method of the present invention, even if the methacrylimide-containing polymer is left to stand for a long period of time after being produced and then molded, a molded product without yellowing can be obtained. It produces industrially valuable effects.

Claims (5)

[Claims] (1) The following general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R represents H or an aliphatic, aromatic, or alicyclic hydrocarbon having 1 to 20 carbon atoms.) When thermoforming a methacrylimide-containing polymer consisting of 2 to 100% by weight of the structural units shown above and 0 to 98% by weight of structural units derived from an ethylenic monomer, the oxygen concentration in the polymer is determined by adjusting the oxygen concentration in the atmosphere. A method for molding a methacrylimide-containing polymer, characterized in that the polymer is molded at an equilibrium concentration or lower at a pressure of 60 mmHg. (2) The method for molding a methacrylimide-containing polymer according to claim 1, characterized in that the polymer is molded after being stored in an inert gas atmosphere with an oxygen partial pressure of 60 mmHg or less. (3) Claim 1, characterized in that the polymer is molded after being stored in a reduced pressure atmosphere with an oxygen partial pressure of 60 mmHg or less.
A method for molding a methacrylimide-containing polymer as described in 1. (4) Oxygen concentration in the polymer is adjusted to 20mm oxygen partial pressure in the atmosphere.
2. The method for molding a methacrylimide-containing polymer according to claim 1, wherein the polymer is molded at a concentration lower than the equilibrium concentration in Hg. (5) The method for molding a methacrylimide-containing polymer according to claim 1, wherein the heating molding is carried out in an inert gas atmosphere.