WO2015172966A1

WO2015172966A1 - Polymer composition comprising a polyester and titanium dioxide

Info

Publication number: WO2015172966A1
Application number: PCT/EP2015/058259
Authority: WO
Inventors: Ronald Michaël Alexander Maria SCHELLEKENS; Esther Wessels
Original assignee: Dsm Ip Assets B.V.
Priority date: 2014-05-15
Filing date: 2015-04-16
Publication date: 2015-11-19

Abstract

A polymer composition comprising: a thermoplastic polyester, 10 - 30 wt.% titanium dioxide, 0.0002 - 0.004 wt.% of an organic red pigment of the group quinacridone based pigment and diazo condensation based pigment, 0.01 - 0.7 wt. % of an optical brightener and/or 0.0005 - 0.004 wt.% of an organic blue pigment.

Description

POLYMER COMPOSITION COMPRISING A POLYESTER AND TITANIUM DIOXIDE

The invention relates to a polymer composition comprising a polyester and titanium dioxide and injection molded parts of that composition.

A composition comprising a polyester and titanium dioxide may have a white color, since titanium dioxide is a white pigment. However it is very difficult or even impossible to obtain a very intense white color, often indicated by arctic white color. It is possible to intensify the white color by increasing the concentration of titanium dioxide in the composition.

However, mechanical properties, especially impact resistance and elongation at break deteriorate and the obtained intensity of the white color is not high enough. Normally this is not because the L-value in the color spectrum (the position at the L-axis according to the CIElab scale, between black and white, also called the lightness) is too low, but because the a-value (the position at the a-axis, between green and red) and the b-value (the position at the b-axis, between blue and yellow) do not have the right value. In that case the composition does not have an arctic white color, but a so-called off-white color.

In order to bring the color of the composition closer to arctic white, an optic brightener may be added. An optical brightener generally reflects the incoming UV-light as a visible blue light. In that way it transfers the b-value from yellow towards blue, so that a neutral b-value may be obtained.

In order to adjust the a-value, a colorant must be used. A problem is that by adjusting the a-value, the L-value and sometimes also the b-value are negatively influenced, so that it is impossible to obtain a composition having an intensely white or even arctic white color.

Object of the invention is to provide a composition not showing this problem. Surprisingly this object is obtained by a polymer composition comprising a thermoplastic polyester,

10 - 30 wt.% titanium dioxide,

0.0002 - 0.004 wt.% of an organic red pigment of the group quinacridone based pigment and diazo condensation based pigment,

0.01 - 0.7 wt. % of an optical brightener and/or

0.0005 - 0.004 wt.% of an organic blue pigment.

With the composition according to the invention an intensive white color or even arctic white color is obtained, with moderate concentration of titanium dioxide. Most likely because the organic red pigment only change the a-value, and not the L-value. Preferably the composition consists of:

a thermoplastic polyester

15 - 25 wt. % titanium dioxide,

0.0002 - 0.002% wt.% of the organic red pigment,

0.01 - 0.5 wt.% optical brightener and/or 0.0005 - 0.002 wt.% of the organic blue pigment,

0 - 10 wt.% additives.

A suitable thermoplastic polyesters that may be used in the composition according to the invention are, for example, polyalkyleneterephthalat.es, polyalkylene naphthalates, and polyalkylene bisbenzoates and any copolymers and any mixtures thereof. These polyesters can be derived from alkane diols and, respectively terephthalic acid, naphthalene dicarboxylic acid and 4,4'- diphenyldicarboxylic acid. Suitably, the polyalkyleneterephthalate is poly(1 ,4- cyclohexane-dimethylene terephthalate) (PCT) or a poly(alkylene terephthalate) based on an aliphatic diol with 2 to 6 carbon atoms, like polyethyleneterephthalate (PET), polytrimethyleneterephthalate (PTT), and poly(1 ,4-butylene terephthalate) or simply called polybutylene terephthalate (PBT). Suitable poly(alkylene naphthalate)s include polyethylenenaphthalate (PEN) and polybutylenenaphthalate (PBN). Suitable polyalkylene bisbenzoates include polyethylenebisbenzoate (PEBB) and

polybutylenebisbenzoate (PBBB). Suitably, these semi-aromatic thermoplastic polyesters comprise a minority content of another dicarboxylic acid or diol. Of these polyesters, PET and PBT, and any mixture or copolymer thereof are preferred. More preferably the thermoplastic polyester is PET.

Surprisingly good results have been obtained if the composition according to the invention contains recycled PET. The use of recycled PET is very advantageous, since it reduces the outlet of carbon dioxide and it also lowers the price of the composition. Normally however it is very difficult to obtain a very white or even arctic white color if recycled PET is used, because recycled PET is somewhat discolored.

Preferably the composition contains more than 20 wt.% of titanium dioxide, more preferably more than 22 wt.%. Suitable titanium dioxides include

Dupont® R-105 and R-104, Kronos® 2220 and 2500 as well as Crenox ® RFK-2.

Preferably the composition contains between 0.05 and 0.3 wt. %, more preferably between 0.07 and 0.2 wt.% of optical brightener. An optical brightener is a compound that transfers UV light into blue light. Examples of optical brighteners include triazine-stilbenes (di,-, tetra- or hexa-sulfonated), benzoxazolines and biphenyl- stilbenes. Specific examples of optical brighteners include 2,5-thiophenediylbis(5-tert- butyl-1 ,3-benzoxazole), 2,2'-(4,4'-diphenol vinyl) dibenzoxazol and 4-(2-Benzoxazolyl)- 4'-(5-methyl-2-benzoxazolyl)stilbene.

Examples of organic blue pigments include Color Index (C.I.) Pigment Blue 28, 29 and 36.

As organic red pigment of the group quinacridone based pigment C.I. Pigment Red 122 is preferably used. As diazo condensation based pigment. C.I.

Pigment Red 214 is preferably used.

Examples of additives include

Examples of additives that may be used in the composition according to the invention include stabilisers, anti-oxidants, colorants, processing aids like a mould-release agent, viscosity-modifiers like a chain extension agent, impact-modifiers, etcetera. If the composition contains a nucleating agent, preferably micro-talcum is used. In case the composition contains at least 20 wt.% of titanium dioxide the composition preferably does not comprise a nucleating agent at all.

It is possible that the composition according to the invention is subjected to a solid state post condensation to increase the mechanical properties.

EXAMPLES. Materials used.

PET, virgin polyethylene terephthalate having a relative viscosity (RSV) of 1.34, deliverd by DSM.

PCR PET, post-consumer recycle (PCR) SC820, RSV 1.49, delivered by INCOM. Ti02, titanium dioxide TiPure R105, delived by DuPont

Nucleating agent microtalc MP 1250, delivered by Barretts Minerals Inc.

Mould release agent Glycolube P deliverd by Lonza

Optical brightener Tinopal OB (OB), deliverd by BASF

Colorants:

C.I. Solvent Violet 36, Macrolex Violet 3R (Violet), delivered by BASF

C.I. Pigment Red 122, PV Fast Pink E (Pink), delivered by Clariant

C.I. Pigment Red 214, PV Fast Red BNP (RED), delivered by Clariant

Preparation of PET composition by compounding.

The polymer compositions were prepared on a ZE40A UTX twin- screw extruder from Berstorff. The barrel temperature was set at 260 - 300 °C, the screw speed was 300 RPM and the yield was 180 kg/hour. Components such as PET, nucleating agent and mould release agent, and colorants were dosed to the hopper as a pre- blend. The titanium dioxide was introduced via a side-feeder into the polymer melt. Extruded strands were cooled in water and granulated.

Preparation of test specimens by Injection moulding.

Plaques for color measurements with dimension 80x80x3 mm have been injection moulded from pre-dried (10 hours at 120 °C under vacuum with nitrogen flow) granulate on an Arburg 1 10 injection moulding machine with 30 mm diameter barrier screw. A nozzle with a length of 60mm was used to inject the material into a mould with high gloss inserts (With ISO 4287 roughness parameter NO, hand polished).

Tensile test bars according to the ISO 527 standard, type 1A, were injection moulded from pre-dried (10 hours at 120 °C under vacuum with nitrogen flow) granulate on an Arburg 1 10 injection moulding machine. Melt temperature settings of

280 - 295°C and mould temperature of 30°C have been used.

TEST METHODS USED Relative solution viscosity

The relative solution viscosity (RSV) was determined in a solution of 0.5 gram of polymer in 100 ml of dichloroacetic acid at 25 °C (method based upon ISO 1628-5). Mechanical properties

The tensile test was carried out at 23°C with the injection moulded ISO 527 type 1 A bars. Testing of the tensile test bars occurred in accordance with the ISO 127 standard. The tensile testing speed was 5 mm/min. Colour measurements

The colour co-ordinates L^*a^*b^* have been determined with the Minolta CM-3700d spectrophotometer using a Xenon light-source, according to ISO 7724-1 -2-3. The colour is measured in reflectance at 23°C on the 80x80x3 mm plaques; a white background, D65 illumination and geometry d/8° with observer 10°, and a round measuring area with a diameter of 25.4 mm have been used

Comparative experiment A A composition was prepared and tested comprising 29.4% virgin PET, 45% PCR PET, 25% Ti02 TiPure R105, 0.1 % Tinopal OB, 0.15% microtalc MP1250, and 0.35% Glycolube P. The color charecteristics are shown in table 1. Comparitative experiments B 1-4

In order to increase the a-value as measured at the sample of comparative example A Macrolex Violet 3R was added to the formulation as described in comparitative example A, at concentration of 0.0005% to 0.0015% . In table 1 is shown that the a-value increases when addition of the colorant, but the L-value decreases significantly.

Examples 1-4

It is show that upon addition of the colorant PV Fast Pink E to the same formulation the a-value improves significantly and, remarkable, the L-value is hardly influenced, or even a slight increase of the L-value is obtained. Furthermore it is shown that a very intensive white colour has been obtained.

Table 1

Violet Pink OB L* a* b*

[%] [%] [ ]

Comp. A 0 0 0,10 97,5 -0,91 -0,04

Comp. B-l 0,0005 0,10 97,0 -0,58 -0,84

B-2 0,0005 - 0,05 96,9 -0,62 -0,19

B-3 0,0010 - 0,05 96,4 -0,37 -0,51

B-4 0,0015 - 0,05 96,0 -0,11

Ex. 1 0,0005 0,10 97,5 -0,43 0,15

Ex. 2 - 0,0005 0,20 97,7 -0,38 -0,90

Ex. 3 - 0,0010 0,20 97,7 0,03 -0,81

Ex. 4 - 0,0015 0,20 97,6 0,22 -0,19 Examples 5.

A composition was prepared and tested comprising 74.3 PCR PET, 25% Ti02 TiPure R105, 0.2% Tinopal OB, 0.0010% PV Fast Pink E, 0.15% microtalc MP1250, and 0.35% Glycolube P. The colour characteristics are shown in table 2.. This example shows that even when the total amount of PET used in the composition is recycled, still a very white colour is obtained

Example 6

In this example a material has been made comparable to example 3. The PV Fast Pink E colorant is replaced by PV Fast Red BNP. This colorant also improves the a-value significantly, while maintaining the high L-value.

Table 2

PCR PET Pink Red OB L* a* b* [%] [ ] [ l [ ]

Ex. 5 75 0,0010 0,20 97,4 -0,24 -0,55

Ex. 6 45 0,0002 0,20 97,6 -0,05 -0,98

Examples 7.

In this example a material has been made comparable to example 3, but omitting the nucleant MP1250 out of the recipe.. Strain at break of this material is considerably higher, see table 3

Table 3

Ex. 3 Ex. 7

MP1250 [%] 0,15 0

L* 97,7 97,4

a* 0,03 0.02

b* -0,81 -0,56

Tensile modulus [MPa] 3790 3225

Yield stress [MPa] 60 53

Strain at break [ ] 5 75

Claims

A polymer composition comprising:

a thermoplastic polyester,

10 - 30 wt.% titanium dioxide,

0.01 - 0.7 wt. % of an optical brightener and/or

0.0005 - 0.004 wt.% of an organic blue pigment.

Composition according to claim 1 , wherein the composition consists of:

a thermoplastic polyester

15 - 25 wt. % titanium dioxide,

0.0002 - 0.002 wt.% of the organic red pigment,

0 - 10 wt.% additives.

Composition according to any one of the preceding claims, wherein the polyester is polyethylene terephthalate.

Composition according to any one of the preceding claims, wherein the polyester is recycled polyethylene terephthalate.

Composition according to any one of the preceding claims, wherein as optical brightener a triazine-stilbene (di,-, tetra- or hexa-sulfonated), a benzoxazoline and/or a biphenyl-stilbene is used.

Composition according to any one of the preceding claims, wherein as organic blue pigment Color Index (C.I.) Pigment Blue 28, 29 and/or 36 is used.

Composition according to any one of the preceding claims, wherein as organic red pigment C.I. Pigment Red 122 and/or 214 is used.

Composition according to the invention according to any one of the preceding claims, wherein the composition contains at least 20 wt. % of titanium dioxide and does not contain a nucleating agent.