GB2294939A - Hot melt ink jet printing composition comprising an oligourea - Google Patents

Abstract

Hot melt ink composition comprises an oligourea, having a melting point of at least 65 DEG C and obtainable by reacting an aliphatic or aromatic mono- or diisocyanate with an at least stoichiometric amount of: (i) a primary or secondary monoamine component; or (ii) a primary or secondary monoamine component followed by another different primary monoamine component; or (iii) a primary or secondary monoamine component, followed by a diprimary diamine component followed by a primary or secondary monoamine component; or (iv) a primary or secondary monoamine component, followed by an alcohol component; the diprimary diamine component being used in an amount of not more than 50% of the stoichiometric amount of amine groups required to react with the isocyanate group(s) on the diisocyanate, together with a colourant.

Description

Hot Melt Ink Jet Printing This invention is concerned with improvements in and relating to materials or compositions for use in hot melt ink jet printing processes.

Ink jet printing generally comprises forming a patterned array of droplets of an ink upon a substrate to form the desired indicia on the substrate. In a hot melt ink jet printing process, the ink is one which is normally solid at ambient temperatures and which is applied to the substrate in molten form so that the droplets solidify on cooling on the substrate.

Typically, the ink employed in hot melt ink jet printing comprises a fusible carrier together with a colourant, i.e. a pigment or dyestuff. Suitable materials for use as or in the vehicles for inks for hot melt ink jet printing (hereinafter, simply, "hot melt inks") should be relatively hard and non-tacky at ambient temperatures whilst being capable of melted to form inks. Suitably, they have a melting point of at least 650C. A wide variety of materials have been proposed for use as vehicles in hot melt inks but there still remains a need for a good, thermally stable material having a relatively sharp melting point.

It has now been found, in accordance with the present invention, that there may be used as hot melt ink vehicles reaction products obtained by reacting a monoisocyanate or diisocyanate with one or more primary or secondary monoamine optionally in combination with a diprimary diamine.

According to one embodiment of the invention, therefore, there is provided a material suitable for use as a vehicle in a hot melt ink, having a melting point of at least 650C and obtainable by reacting an aliphatic or aromatic mono- or di- isocyanate with an at least stoichiometric amount of: (i) a primary or secondary monoamine component; or (ii) a primary or secondary monoamine component followed by another different primary monoamine component; (iii) a primary or secondary monoamine component, followed by a diprimary diamine component, followed by a primary or secondary monoamine component; or (iv) a primary or secondary monoamine component, followed by an alcohol component; the diprimary diamine being used in an amount not more than 50% of the stoichiometric amount of amine groups required to react with the isocyanate group(s) on the isocyanate.

As noted above, it is a requirement of the present invention that the material obtained (hereinafter simply referred to as an "oligourea") have a melting point of at least 650C (The term 'melting point' as used herein means the melting point as determined by the ball and ring method). It should be noted that not all materials obtainable in accordance with the process outlined above will have melting points of at least 650C. Our experiments have shown that there is wide variation in melting point and attempts to predict whether a particular reaction product will have the desired melting point, for example having regard to the molecular weight of the component reactants or the possible molecular weight of the final product, simply do not yield meaningful results.However, of course, to determine the melting point of any particular material is a matter for simple routine experiment and trial.

Suitable isocyanates for use in the preparation of the oligourea include octadecylmonoisocyanate, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hexamethylene- 1,6-diisocyanate, napthylene-1,5-diisocyanate, 3,3'-dimethoxy-4,4'biphenyldiisocyanate, 3,3'-dimethyl-4,4'- biphenyldiisocyanate, phenylene di- isocyanate, 4,4' -biphenyldiisocyanate, isophorone di- isocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate, trimethylhexamethylene diisocyanate, and tetramethylene xylene diisocyanate. Of these diisocyanates, the aliphatic diisocyanates are generally preferred and, in particular, isophorone diisocyanate, trimethylhexamethylene diisocyanate and octadecylmonoisocyanate have been found to give particularly useful oligoureas.

A wide variety of primary and secondary amines may be used to produce the oligoureas, e.g. C1 to C22 monoamines such as ethylamine, octylamine, hexadecylamine, octadecylamine, di - n- butylamine, neopentadiamine, di-n-tallow-amine, di-n-cocoamine and N-methyloctadecylamine.

Suitable diprimary diamines include isophorone diamine, neopentane diamine, hexamethylene diamine, ethylene diamine, polyoxypropylene diamines, 2-methylpentamethylene diamine and 1,12-dodecane diamine.

The reaction between the isocyanate and the amine component is usually carried out in the absence of a catalyst, but catalysts such as dibutyl tin dilaurate and stannous octoate may be used to ensure that the reaction reaches completion.

The molecular weight of the final oligourea is suitably from 250 to 2000,preferably from 250-750.

For some applications of hot melt inks, it is desirable that the vehicles, the oligoureas, be clear.

Again, it is virtually impossible to predict whether any particular oligourea produced in accordance with the invention will, or will not, have the desired optical properties in this respect. However, here again it is a matter of simple routine trial and experiment and many of the oligoureas do have the desired optical properties. Similarly, it is generally desirable that the oligoureas should have relatively low viscosities (e.g. less than 200 cp at 125at) and, here again, it is difficult to make predictions as to the viscosity of any particular oligourea material.

The oligoureas of the invention are used as vehicles, or components of the vehicles, of hot melt inks and, in addition to the oligoureas, such inks will generally comprise colourants such as pigments or dyestuffs. Further, other conventional additives such as antioxidants etc, may also be present. Generally the vehicle (oligourea) will form from 80 to 95% by weight, especially 90 to 95% by weight of any ink with viscosity and compatibility improving additives forming the bulk of the remainder and the other additives (colorants, etc.) being present in relatively small amounts, e.g. to a total of not more than 10% by weight of the ink.

In order that the invention may be well understood the following Examples are given by way of illustration only.

Example 1 1 molar part of trimethylhexamethylene diisocyanate was charged into a flask and heated to 850C with stirring and under inert conditions. 2 molar parts of octadecylamine were carefully added to the contents of the flask over a period of one and a half hours whilst keeping the temperature below 1000C until no further exotherm occurred. The temperature was then raised to 1300C and held until the isocyanate value of the material was less than 30 ppm.

The resulting product had a ball and ring melting point; of 1050C a relative viscosity of 190 cp.; and was clear and stable at elevated temperature.

Example 2 1.6 molar parts of hexadecylamine, 0.4 molar parts of di-n-tallaow amine and 1 molar part of trimethylhexamethylene diisocyanate were reacted following the procedure described in Example 1. The resulting product had a ball and ring melting point of 790C and a relative viscosity of 140 cp. The product was translucent and heat stable.

Example 3 Octadecylamine, octadecanol and trimethylhexamethylene diisocyanate were reacted in accordance with the procedure described in Example 1 except that stannous octoate was used as catalyst when adding the alcohol component to the reaction mixture.

The resulting product had a ball and ring melting point of 1010C and relative viscosity of 140 cp. It was a translucent product which was heat stable.

Example 4 2 molar parts of octadecylmonoisocyanate and 1 molar part of neopentadiamine were reacted following the procedure described in Example 1 to give a product having a ball ring melting point of 800C and a relative viscosity of 10 cp. The product was translucent and heat stable.

Example 5 1 molar part of octadecylamine, 1 molar part of octadecylmonoisocyanate were reacted together following the general procedure of Example 1. The resulting product had a ball and ring melting point of 118 C and a relative viscosity of 20 cp.

Claims (2)

CLAIMS:

1. A hot melt ink comprising a colorant together with, as a vehicle, a material having a melting point of at least 650C and obtainable by reacting an aliphatic or aromatic mono- or di- isocyanate with an at least stoichiometric amount of: (i) a primary or secondary monoamine component; or (ii) a primary or secondary monoamine component followed by another different primary monoamine component; (iii) a primary or secondary monoamine component, followed by a diprimary diamine component followed by a primary monoamine component; or (iv) primary or secondary monoamine component, followed by an alcohol component; the diprimary diamine component being used in an amount of not more than 50% of the stoichiometric amount of primary amine groups required to react with the isocyanate groups on the diisocyanate.

2. A hot melt ink as claimed in claim 1 substantially as hereinbefore described with reference to the Examples.