GB1581953A - Method for clear-colouring of linear aromatic polyester - Google Patents

Description

(45) METHOD FOR CLEAR-COLOURING OF LINEAR AROMATIC POLYESTER (71) We, DAINIPPON INK AND CHEMICALS, INC., a Japanese Body Corporate, of 35-58, 3-chome, Sakashita, Itabashi-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a colouring method, and more soecifically, to a method for clearcolouring linear aromatic polyesters.

Linear aromatic polyesters are used to produce textile products, film products and other molded products. For example, polyethylene terephthalate is commercially utilised in the production of fibres and films, and polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate, in the production of other shape articles.

The basic requirements for colouration of linear aromatic polyesters using pigments are that (1) the pigments should have good fastness characteristics, for example, they must withstand high melting temperatures (up to 3000C) and have superior fastness to light and sublimation, and (2) the pigment particles should be finely and uniformly dispersed in the polyesters without being agglomerated.

In recent years, the consumers have not been content merely with pigment-coloured nontransparent pastel-like colours, but tended to demand products having brilliant and clear colours. To obtain clear-coloured linear aromatic polyesters, a method of "dope dyeing" was suggested which involves mixing a dye with a polyester, and melting the mixture.

Japanese Patent Publication No. 26095/68 and U.S. Patent Specification No. 3,401,142 disclose some anthraquinonic dyes as suitable for use in dope dyeing.

The present inventors have found that instead of such dyes, certain pigments give brilliant and clear colours when used to colour linear aromatic polyesters.

Thus, the present invention provides a method for clear-colouring linear aromatic polyesters, which comprises mixing the pigment of formula (I) below,

with a linear aromatic polyester; and then heating the mixture to the melting temperature of the polyester to dissolve or substantially dissolve the pigment in the polyester.

This pigment (1) is described in "Colour Index, 3rd Edition, Volume 3" (published by The Society of Dyers and Colourists with acknowledgement to The American Association of Textile Chemists and Colourists) as (1) C.I. Pigment Red 194. This pigment has a melting point of at least 3000C, and is widely used as a colouring agent for printing inks, paints and lacquers. It is known that this pigment may be used for dyeing cotton as a vat dye, or for colouring polyolefins, rubber, vinyl plastics, etc.

Investigations of the pigment of the present invention show that when the pigment of the Formula (I) is used for colouring polypropylene, the pigment particles disperse in polvDropylene to afford a dull red colour or a dull reddish violet colour, and when used for colouring 6-nylon, they discolour at the time of melting 6-nylon. It was found, surprisingly, that when this pigment is used to colour linear aromatic polyesters whose melting temperatures are as high as 250 to 3000C, the pigment dissolves in the polyesters during melting, and no pigment particle is seen to disperse; and that the colour imDarted is a clear brilliant red colour or reddish violet colour, and the coloured polyesters have superior fastness to heat, light and to sublimation.

The linear aromatic polyesters that can be coloured by the method of this invention are linear polyalkylene terephthalates obtained by the reaction of terephthalic acid or dialkyl terephthalates with glycols of the formula HOCH2OH, n being an integer of 2 to 10, or 1 ,4-di ( hydroxymethyl ) cyclohexane.

These polyesters have long been known as materials for fibres and films, and methods for their production are described, for example, in U.S. Patent Specification No.

2,475,319 (Whinfield) and U.S. Patent Speci fiction No. 3,047,539 (Pengilly).

The linear aromatic polyesters, namely linear polyalkylene terephthalates containing 2 to 10 alkylene groups, as used in this application are also meant to include copolyesters based on these polyesters. These copolyesters can be obtained by replacing the starting terephthalic acid component partly by another dicarboxylic acid or hydroxycarboxylic acid, and/or the starting glycol partly by another glycol. Examples of the other dicarboxylic acid or hydroxycarboxylic acid are isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, hydroxyethoxybenzoic acid, hydroxypropoxybenzoic acid, p-hydroxybenzoic acid, adipic acid, and sebacic acid.

Typical examples of the linear aromatic polyesters are polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and copolyesters resulting from the replacement of a part of the constituent monomers by other monomers.

The linear aromatic polyesters used in this invention have an intrinsic viscosity, measured at 250C in a mixture of equal amounts of tetrachloroethane and phenol, of 0.4 to 1.2.

The method of this invention is achieved by mixing the pigment with a linear aromatic polyester, advantageously mixing the finely divided pigment with a chip-like or granular linear aromatic polyester, and heating the mix ture to the melting temperature of the poly ester, preferably to 250 to 300 C, to dissolve or substantially dissolve the pigment in the polyester.

The amount of the pigment to be mixed with the linear aromatic polyester is usually up to 1% by weight based on the total weight of the polyester and the pigment. When the operability of the coloured polyester in spinning and other fabrication processes is considered, the amount of the pigment should desirably be 0.01 to 0.5% by weight.

The coloured linear aromatic polyester produced by the method of this invention contains no detectable pigment particle, and has a brilliant and dear colour. It also has superior fastness to heat, light and sublimation.

If desired, other pigments such as C.I.

Pigment Red 87 and/or C.I. Pigment Violet 36 (as described in "Colour Index", 3rd Edition, Volume 3), fillers, reinforcing agents or stabilisers, may also be incorporated.

In this connection it is to be noted that our co-pending Application No. 30659/77 (Serial No. 1,581,952) describes and claims a method similar to the method of the present invention wherein the pigment is selected from certain thioindigo pigments including C.I. Pigment Red 87 and C.I. Pigment Violet 36.

The following Examples illustrate the present invention without any intention of limiting it.

All parts in these Examples are by weight.

Example 1.

0.5 parts of C.I. Pigment Red 194 and 99.5 parts of polyethylene terephthalate having an intrinsic viscosity of 0.70, were mixed and dried at 1800 C and 0.01 mmHg for 5 hours.

The mixture was melt-spun in a customary manner at 3000 C with a residence time of 3 minutes to afford 3-denier coloured filaments.

The characteristics of the coloured filaments are shown in the following table.

Example 1 Pigment C.l. Pigment Red 194 Color of the colored filaments Red Orange State of the pigment in the No pigment polyester (*1) particle observed light (*2) 7 8 heat (*3) 4 - 5 washing (*4) change 4 - 5 staining 4-5 a organic change 4-5 solvent (perchloro ethylene) staining 4 - 5 (*5) (nylon) Sublimation (*6) ) 3 4 Rubbing (*7) wet 5 dry 5

Note (*1): Ten milligrams of a coloured filament sample was melted. It was placed at 2900 C between two thin-layer glass plates and observed with a 400X microscope.

(*2): Measured on a blue scale in accordance with JIS L 0483-71 (Xenon arc).

(*3): A coloured filament obtained by spinning in the same way as described above except that the residence time was changed to 15 minutes was compared with a gray scale for assessing change in colour.

(*4): Measured on a gray scale in accordance with JIS L-0844-73 (700 C + 2" C, 45 min.).

(*5): Measured on a gray scale in accordance with JIS L 0860-74 (400 C + 20 C, 30 min.).

(*6): A sample coloured filament was wrapped by a polyester cloth, and allowed to stand for 90 minutes in a hot air dryer at 1800 C, and then the stained state of the poly ester cloth was measured by using a gray scale for assessing stain in colour.

(*7): Measured in accordance with JIS L 0849-71 using a gray scale for assessing stain in colour.

Example 2.

C.I. Pigment Violet 36 (0.2 part), 0.3 part of C.I. Pigment Red 194 and 99.5 parts of polyethylene terephthalate (intrinsic viscosity 0.68) were uniformly mixed, and dried at 120"C and 0.01 mmHg for 16 hours. The mixture was spun at 2900 C in a customary manner to afford 6-denier filaments having a brilliant red colour. No particle of the pig ments was detected by observation with 400X microscope.

The filaments had substantially the same fastness characteristics as the filaments obtained in Example 1.

Example 3.

C.I. Pigment Red 87 (2 parts), 6 parts of C.I. Pigment Red 194, 2 parts of carbon black and 90 parts of polyethylene terephthalate (in tlinsic viscosity 0.70) were mixed, and dried at 180"C and 0.01 mmHg for 5 hours. The mixture was extruded at 2900 C to afford a master batch of 10% pigment concentration.

Five parts of the master batch was mixed with 95 parts of polyethylene terephthalate, and the.

mixture was dried at 1300 C and 0.01 mmHg for 10 hours. The dry mixture was spun at 290 C and drawn in a customary manner to obtain 10-denier filaments, having a brown colour. Ten milligrams of a coloured filament was melted and placed at 2900 C between two thin layer glass plates and observed with a 400X microscope. Only carbon black particles were seen. The resulting filaments had substantially the same fastness characteristics as the filaments obtained in Example 1.

Example 4.

C.I. Pigment Red 194 (0.3 part) and 99.7 parts of reinforced polybutylene terephthalate (intrinsic viscosity 0.7, containing 30% by weight of glass fibres) were mixed, and dried at 120"C under atmospheric pressure for 4 hours. The dried mixture was molded at 2500 C to afford plates uniformly coloured red violet.

WHAT WE CLAIM IS: 1. A method for clear-colouring of linear aromatic polyesters, which comprise mixing a pigment of the formula

with a linear aromatic polyester, and heating the mixture to the melting temperature of the polyester to dissolve or substantially dissolve the pigment in the polyester.

2. The method of claim 1 substantially as herein described in Example 1.

3. The method of claim 1 substantially as herein described in Example 4.

4. Linear aromatic polyesters coloured by the method of claim 1.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. fastness characteristics as the filaments obtained in Example 1. Example 3. C.I. Pigment Red 87 (2 parts), 6 parts of C.I. Pigment Red 194, 2 parts of carbon black and 90 parts of polyethylene terephthalate (in tlinsic viscosity 0.70) were mixed, and dried at 180"C and 0.01 mmHg for 5 hours. The mixture was extruded at 2900 C to afford a master batch of 10% pigment concentration. Five parts of the master batch was mixed with 95 parts of polyethylene terephthalate, and the. mixture was dried at 1300 C and 0.01 mmHg for 10 hours. The dry mixture was spun at 290 C and drawn in a customary manner to obtain 10-denier filaments, having a brown colour. Ten milligrams of a coloured filament was melted and placed at 2900 C between two thin layer glass plates and observed with a 400X microscope. Only carbon black particles were seen. The resulting filaments had substantially the same fastness characteristics as the filaments obtained in Example 1. Example 4. C.I. Pigment Red 194 (0.3 part) and 99.7 parts of reinforced polybutylene terephthalate (intrinsic viscosity 0.7, containing 30% by weight of glass fibres) were mixed, and dried at 120"C under atmospheric pressure for 4 hours. The dried mixture was molded at 2500 C to afford plates uniformly coloured red violet. WHAT WE CLAIM IS:

1. A method for clear-colouring of linear aromatic polyesters, which comprise mixing a pigment of the formula

with a linear aromatic polyester, and heating the mixture to the melting temperature of the polyester to dissolve or substantially dissolve the pigment in the polyester.

2. The method of claim 1 substantially as herein described in Example 1.

3. The method of claim 1 substantially as herein described in Example 4.

4. Linear aromatic polyesters coloured by the method of claim 1.