KR20090008825A - Method for preparing polyester/polycarbonate blend with advanced color stability - Google Patents

Abstract

A method for preparing polyester/polycarbonate blend is provided to improve heat resistance and color stability by compounding PET and PC and additionally compounding the PET component modified with CHDM. A method for preparing polyester/polycarbonate blend comprises a step for the PET / PC blend by compounding the polyethylene terephthalate(PET) and polycarbonate(PC); and a step for compounding the obtained PET / PC blend and a large amount of cyclohexanedimethanol(CHDM) glycol-modified PET. In the PET / PC blend, the content of PC is 10-70 weight%. The content of the large amount of CHDM glycol-modified PET is 0.2-2.5 times based on the weight ratio of PC. The large amount of CHDM glycol-modified PET is the PET copolymerized with 30-80mol% CHDM based on the diol component. In the large amount of CHDM glycol-modified PET, the content of the ethylene glycol is 20-70mol% based on the diol component.

Description

Method for Preparing Polyester / Polycarbonate Blend with Advanced Color Stability

The present invention relates to a method for producing a polyester / polycarbonate blend having excellent color stability, and more particularly, to a polyester / polycarbonate blend capable of improving heat resistance and color stability compared to a conventional polyester / polycarbonate blend. It is about a method.

Since polyester has excellent mechanical strength, heat resistance, transparency, and gas barrier property, polyester is most suitable as a material for beverage filling containers such as juices, soft drinks, carbonated drinks, and packaging films, audio, and video films. Is being used. It is also used in large quantities worldwide as industrial materials such as medical fibers and tire cords. Polyester sheets and sheet materials have good transparency and excellent mechanical strength, and are widely used in materials such as cases, boxes, partitions, store shelves, protective panels, blister packaging, construction materials, interior and exterior materials, and the like. As the use of a new polyester, which has recently attracted attention, after molding a thick plastic sheet, there are an increasing number of cases of using it as a building interior material, molded signboard, and the like. However, polyester has a lower heat distortion temperature (HDT) than other materials used for sheet, such as acryl (PMMA) or polycarbonate (PC), so that the outdoor exterior material has a severe seasonal change in temperature. In some cases, it is not suitable for use. Thus, various technical attempts have been made to improve the heat resistance of polyester, and among them, there is a blending technique with a PC.

However, since PET and PC have different melt viscosity and molecular structure, it is difficult to improve heat resistance by simply blending them. PET, a representative crystalline polymer, increases its mechanical strength in the blend and gives toughness to the entire polymer backbone by its crystal structure. Among crystalline PET, homopolyester has a higher crystallization rate than copolyester, and thus exhibits high heat deflection temperature (HDT) and improves blend heat resistance by distributing PET into domains of tens to hundreds of nanometers in the blend matrix. Contribute to. In this case, reducing the size of the domain and increasing the distribution improves not only the transparency but also the heat resistance of the blend, and the heat resistance is further affected by the distribution of the domain.

 Techniques for using copolymers or various complex catalysts to solve the heat resistance problem of PET / PC blends are known. U.S. Patent No. 3,864,428 describes a technique for blend composition of polyester and PC, while U.S. Patent No. 4,879,355 makes a copolymer of PET and bisphenol-A and introduces it to the blend of PET and PC, thereby providing transparency and heat resistance. Techniques to improve the system have been introduced. Also recently disclosed are techniques for blending PC and massive CHDM glycol modified polyesters, such as in US Pat. No. 5,942,585. On the other hand, US Patent No. 6,723,768 B2 on the color stability of the polyester / PC blend confirms that the color stability of the blend is improved when the titanium content is within 30 ppm, and the yellowing problem of the blend is related to the titanium content in each polymer. A close relationship is illustrated.

It is therefore an object of the present invention to provide a process for the preparation of polyester / polycarbonate blends which can improve the heat resistance (HDT) and color stability while maintaining excellent moldability.

Another object of the present invention is to provide a process for producing polyester / polycarbonate blends with excellent color stability by blending three or more blend components in a specific order and method.

In order to achieve the above object, the present invention comprises the steps of: (a) compounding polyethylene terephthalate (PET) and polycarbonate (PC) to obtain a PET / PC blend; And (b) compounding the obtained PET / PC blend with a large amount of cyclohexanedimethanol (CHDM) glycol modified PET, wherein the content of PC in the PET / PC blend is 10-70% by weight, wherein The content of CHDM glycol modified PET is 0.2 to 2.5 times by weight relative to PC, and the large amount of CHDM glycol modified PET is PET in which CHDM is copolymerized with 30 to 80 mol% based on the diol component, and in the large amount of CHDM glycol modified PET, The content of ethylene glycol provides a method for producing a polyester / polycarbonate blend, which is 20 to 70 mol% with respect to the diol component. Here, the PET is a PET consisting of terephthalic acid, ethylene glycol and / or alkylene glycol of 3 to 6 carbon atoms, or isophthalic acid, CHDM or diethylene glycol in the PET component, the acid (acid) or diol component It may be 1 to 10 mol% copolymerized PET.

Hereinafter, the present invention will be described in more detail.

Usually, blending polyester and polycarbonate reduces heat resistance, where the heat resistance tends not to be proportional to the blend composition ratio. In the present invention, in blending polyester and polycarbonate, it has an optimal composition that can overcome the phenomenon that the heat resistance is not proportional to the blend composition.

In general, PC does not contain a metal component, and in the case of PET, an antimony-based organometallic component is used as a catalyst, whereas in some PET or glycol-modified poly (1,4-cyclohexylenedimethylene terephthalate) In the present invention, a titanium-based organometallic component is used as a catalyst for the polymerization reaction, and in the present invention, PET and PC without titanium component are blended first, and then the blend obtained here is blended with PCTG containing titanium component again. Through, it is possible to obtain a polyester / polycarbonate blend with more excellent color stability.

The blend of PCTG and PC has the heat resistance of PC and the softness of PCTG, where PCTG is CHDM glycol modified PET, a copolyester based on terephthalic acid, ethylene glycol and cyclohexanedimethanol (CHDM). Regarding PCTG / PC blends, researches to improve compatibility between the two resins have been actively conducted since the 80's. PCTG / PC blends may exhibit complementary new properties depending on the composition of each component. At the same time, there is a side effect that the color stability is lowered by the interaction of each component. Particularly in the case of PCTG / PC blends, which have undergone a relatively long residence time, yellowing occurs when the blend color changes yellowish. In the manufacturing method according to the present invention, the yellowing phenomenon can be minimized by first compounding PET and PC and then blending it again with PCTG.

Specifically, the method for producing a polyester / polycarbonate blend according to the present invention comprises the steps of: (a) compounding PET and PC to obtain a PET / PC blend; And (b) compounding the obtained PET / PC blend with a large amount of CHDM glycol modified PET.

As the PET component used as the main material in the present invention, PET composed of terephthalic acid, ethylene glycol and / or alkylene glycol having 3 to 6 carbon atoms may be used, or isophthalic acid, CHDM or diethylene for the PET component. PET copolymers of small amounts of glycol may be used. Here, when isophthalic acid is copolymerized, the content thereof is 1 to 10 mol% with respect to the total acid component of the copolymerized PET, and when CHDM or diethylene glycol is copolymerized, the content is the total diol component of the copolymerized PET. 1 to 10 mol% relative to.

The PC may use a variety of general-purpose extrusion and injection polymer prepared by polymerizing bisphenol-A as a basic component. The content of PC is 10 to 70% by weight, preferably 10 to 50% by weight relative to the PET / PC blend. If the content of the PC is less than 10% by weight, the improvement of heat resistance is insignificant, and if it exceeds 70% by weight, the meaning and economical efficiency of the blend of PC to PET are lowered.

A large amount of CHDM glycol modified PET (PCTG), which is added after blending the PET component and the PC component, is used in a weight ratio of 0.2 to 2.5 times, preferably 0.5 to 2.0 times, relative to the PC. When the amount of the large amount of CHDM glycol modified PET is less than 0.2 times by weight relative to the PC, the effect of improving transparency is insignificant, and even when more than 2.5 times is added, no further improvement in transparency can be expected, and only manufacturing cost is increased. I can't. The massive CHDM glycol modified PET is composed of CHDM and ethylene glycol as a diol component and terephthalic acid as an acid component, and the content of the CHDM is 30 to 80 mol% based on the total diol component of the large amount of CHDM glycol modified PET. The content of ethylene glycol in the massive CHDM glycol modified PET is 20 to 70 mol% based on the diol component. If the content of the CHDM is less than 30 mol% or more than 80 mol%, there is a problem that the transparency of the blend product is impaired.

As used herein, the polyester-based polymer, that is, the PET and the large amount of CHDM glycol-modified PET are polymerized using a commercially available organic-inorganic catalyst such as antimony, cobalt, germanium, titanium, calcium, aluminum, etc. desirable.

When molding the polyester / polycarbonate blend of the present invention as described above, the molded transparent polyester has a haze value of 30% or less and a heat deflection temperature (HDT) of 75 ° C based on a 3 mm thick specimen. As mentioned above, it is excellent in transparency and heat resistance simultaneously.

In the method for producing a polyester / polycarbonate blend according to the present invention, by compounding PET and PC first, and then further compounding the PET component modified with CHDM, heat resistance and color stability can be improved, and the existing blend Can be easily and economically applied to applications where use has been limited due to poor color stability.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by these examples.

PET used in Examples and Comparative Examples below is SKYPET BL grade produced by SK Chemical (hereinafter Component A, isophthalic acid is copolymerized 2 to 3 mol% with respect to the total acid, CHDM is 3 to 10 mol with respect to the total diol % Copolymerized PET), PC product (melt index (MI): 30, component B) produced by LGDOW was used as PC, and J2003 grade (CHDM content produced by SK Chemicals) was used as a large amount of CHDM modified polyester. 50 to 80 mol%, hereinafter component C) were used for the diol component.

Comparative Example 1

5 kg of component A dried at 160 ° C. for 5 hours using a dehumidifying dryer, 4 kg of component B dried at 120 ° C. for 5 hours in the same dehumidifying dryer, and 1 kg of component C dried at 70 ° C. for 5 hours using the same dehumidifying dryer. It was put in a dehumidified container, tumbling for about 3 minutes, and mixed sufficiently. The mixed raw materials were compounded under a condition of 270 ° C. and 50 rpm through a Hake Extruder manufactured by Hake Corporation, to prepare a blend chip. Using the prepared blend chip was injected using a cold runner (cold runner) type water-cooled mold that can produce a specimen of 12mm x 120mm in the same thickness as the 3.0mm thick, 40mm x 40mm specimen. At this time, the injection machine used had a screw L / D of 23 and a compression ratio of 3, and measured the color value of the transparent injection plate in the transmissive mode by using the transparency and color B (Nippon Denshoku's 300A transmittance meter) for the injected specimen. The higher the color B value of 0, the greater the yellowness.) And the heat deflection temperature (HDT) were measured and the results are shown in Table 1 below.

[Comparative Examples 2 to 3]

As shown in Table 1, except that the amount of the component A, component B and component C were used, the specimen was injected in the same manner as in Comparative Example 1, and the transparency, color B and heat deformation temperature of the injected specimen were Was measured and the results are shown in Table 1 below.

Example 1

5 kg of Component A dried at 160 ° C. for 5 hours using a dehumidifying dryer and 4 kg of Component B dried at 120 ° C. for 5 hours in the same dehumidifying dryer were placed in a sufficiently dehumidified container and tumbled for about 3 minutes to mix well. The mixed raw materials were compounded at 270 ° C. at 50 rpm through a Haake Extruder to obtain 9 kg of PC / PET blend. The obtained PC / PET blend and 1 kg of component C, dried at 70 ° C. for 5 hours in a dehumidifying dryer, were put in a sufficiently dehumidified container, tumbled for about 3 minutes, and mixed sufficiently. The prepared material was compounded at 270 ° C. and 50 rpm using a Haake Extruder to prepare a blend chip. Using the prepared blend chip was injected using a cold runner type water-cooled mold, which can produce a 12mm x 120mm specimen with the same thickness as the 3.0mm horizontal, 40mm x 40mm specimen. At this time, the injection machine used was L / D of the screw 23, the compression ratio was 3, and measured the transparency, the color B and the heat deformation temperature for the injected specimen is shown in Table 1 below.

[Examples 2 to 3]

As shown in Table 1 below, except that the amounts of the components A, B and C were used, the specimens were injected by blending in the same procedure and method as in Example 1, and the transparency of the injected specimens, Color B And the heat distortion temperature was measured and the results are shown in Table 1 below.

Component A Component B Component C Haze (%) Color-b HDT (℃) Comparative Example 1 5 kg 4 kg 1 kg 35 6.7 111 Comparative Example 2 5 kg 3 kg 2 kg 7 4.2 98 Comparative Example 3 7 kg 2 kg 1 kg 9 2.1 75 Example 1 5 kg 4 kg 1 kg 29 5.9 114 Example 2 5 kg 3 kg 2 kg 6 3.8 102 Example 3 7 kg 2 kg 1 kg 7 1.9 79

Referring to Table 1 above, in the case of further compounding the PET and PC according to the present invention, and then further compounding the copolyester material modified with CHDM (Example), the compound of the three components at once Compared to the case (comparative example), the color b (color b) value is significantly improved when the same composition, and also shows a high heat distortion temperature (HDT), it can be seen that excellent heat resistance.

Claims (5)

(a) compounding polyethylene terephthalate (PET) and polycarbonate (PC) to obtain a PET / PC blend; And (b) compounding the obtained PET / PC blend with a large amount of cyclohexanedimethanol (CHDM) glycol modified PET, The content of PC in the PET / PC blend is 10 to 70% by weight, the content of the large amount of CHDM glycol modified PET is 0.2 to 2.5 times by weight relative to PC, and the large amount of CHDM glycol modified PET is a diol component of CHDM. It is 30 to 80 mol% copolymerized PET, and the content of ethylene glycol in the large amount of CHDM glycol modified PET is 20 to 70 mol% based on the diol component. The method of claim 1, wherein the PET is a terephthalic acid, ethylene glycol and / or PET consisting of alkylene glycol having 3 to 6 carbon atoms, or isophthalic acid, CHDM or diethylene glycol in the PET component, acid (acid) Or 1 to 10 mol% copolymerized PET with respect to the diol component. According to claim 1, wherein the content of PC in the PET / PC blend is 10 to 50% by weight, the content of the large amount of CHDM glycol modified PET is 0.5 to 2.0 times the weight ratio of the polyester / polycarbonate blend of PC Manufacturing method. The method of claim 1, wherein the polyester-based polymer is polymerized using a polymerization catalyst selected from the group consisting of antimony, cobalt, germanium, titanium, calcium and aluminum-based polyester / polycarbonate blend Way. A polyester / polycarbonate blend having a haze of 30% or less and a heat distortion temperature (HDT) of 75 ° C. or more based on a 3 mm thick specimen obtained by molding the polyester / polycarbonate blend of claim 1.