WO1996028762A1

WO1996028762A1 - Liquid photocurable compositions

Info

Publication number: WO1996028762A1
Application number: PCT/GB1996/000517
Authority: WO
Inventors: Ajay Haridas Popat; John Robert Lawson; Colin Henry Mclean
Original assignee: Zeneca Limited
Priority date: 1995-03-11
Filing date: 1996-03-06
Publication date: 1996-09-19
Also published as: AU4887096A; GB9504996D0

Abstract

A liquid composition comprising: a) 5 to 25 parts of a monomeric aliphatic or cycloaliphatic di(meth)acrylate having a MW of not more than 800; b) 2 to 20 parts of a monomeric poly(meth)acrylate having a functionality of at least 3 and a MW of at least 610; c) 12 to 40 parts of a urethane(meth)acrylate having a functionality of 2 to 4 and a MW of 400 to 10,000; d) 35 to 70 parts of a monomeric or oligomeric di(meth)acrylate based on bisphenol A or bisphenol F; and e) 0.1 to 10 parts of a photoinitiator; wherein all parts are by weight, the total number of parts of a) + b) does not exceed 30 and the total number of parts of a) + b) + c) + d) + e) add up to 100. The compositions are suitable for the stereolighographic production of three-dimensional solid articles such as mechanical parts and models of body parts.

Description

Liquid photocurable compositions.

This invention relates to photocurable compositions, to a process for their polymerisation by means of actinic radiation, to a process for the production of three-dimensional articles from the compositions and to articles so prepared.

It is known that complicated three-dimensional articles can be produced from liquid photocurable compositions by means of

stereolithography. One such process is described in Hull's US Patent 4,575,330. Articles are built up in layers, each new curable layer of resin being firmly attached to the preceding pre-cured layer by preliminary curing by means of UV/VIS light. The overall construction of the three-dimensional article is normally be controlled by computer.

Photocurable compositions and their use as coating agents, adhesives and photoresists are known. However, the majority of such compositions are not suitable for the production of solidified three-dimensional articles by stereolithography because some are too viscous, whilst others are insufficiently light-sensitive, cure slowly or suffer from excessive shrinking or curling when they are cured.

Ideally photocurable compositions for stereolithography cure reasonably quickly and have a small volume shrinkage in the transition from the liquid to the solid state. The so-called "curl factor" is often quoted as a measure of shrinkage induced deformation and a curl factor of 30% is considered by many as being the maximum acceptable, depending on what the article is, and curl factors of below 20% are preferred.

There is a need for photocurable compositions which do not have an excessive curl factor or high viscosity. Compositions of low viscosity are desirable in stereolithography because they allow rapid recoating of submerged models between curing layers, air bubbles in the composition disperse more quickly and drainage of the final model is facilitated.

Canadian Patent application 2028541 suggests photocurable compositions for stereolithography. Whilst these compositions do work they tend to have a high viscosity. The Examples in CA 2028541 quote viscosities of between 1510 and 6700 mPa.s at 30C. According to the present invention there is provided a liquid composition comprising:

a) 5 to 25 parts of a monomeric aliphatic or cycloaliphatic

di(meth)acrylate having a MW of not more than 800;

b) 2 to 20 parts of a monomeric poly(meth)acrylate having a

functionality of at least 3 and a MW of at least 610;

c) 12 to 40 parts of a urethane(meth)acrylate having a

functionality of 2 to 4 and a MW of 400 to 10,000;

d) 35 to 70 parts of a monomeric or oligomeric di(meth)acrylate based on bisphenol A or bisphenol F; and

e) 0.1 to 10 parts of a photoinitiator;

wherein all parts are by weight, the total number of parts of a) + b) does net exceed 30 and the total number of parts of a) + b) + c) + d) + e) add up to 100.

The liquid composition of the invention preferably comprises or consists essentially of 6 to 22 parts, more preferably 6 to 20 parts of component a); 3 to 18 parts, more preferably 3 to 15 parts of component b); 15 to 38 parts, more preferably 16 to 35 parts of component c); 40 to 68 parts, more preferably 42 to 65 parts of component d); and 1 to 9 parts, more preferably 2 to 8 parts, especially 3 to 7 parts of

component e); wherein all parts are by weight, the total number of parts of a) + b) does not exceed 30 and the total number of parts of a) + b) + c) + d) + e) add up to 100.

In a particularly preferred embodiment the liquid composition of the invention comprises or consists essentially of 6 to 20 parts of component a); 3 to 15 parts of component b); 16 to 35 parts of component c); 42 to 65 parts of component d); and 3 to 7 parts of component e); wherein all parts are by weight, the total number of parts of a) - b) does not exceed 30 and the total number of parts of a) + b) + c) + d) + e) add up to 100.

Component a) is preferably a di(meth)acrylate ester of an

aliphatic or cycloaliphatic diol, for example a di(meth)acrylate ester of 1,3-butylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 401, polyethylene glycol 600, tripropylene glycol, ethoxylated or propoxylated neopentyl glycol,

1,4-dihydroxymethylcyclohexane, 1,4-dihydroxycyclohexane, 2,2-bis-(4- hydroxycyclohexyl)-propane, bis-(4-hydroxycyclohexyI)-methane or a mixture thereof.

Component b) preferably has a MW (i.e. molecular weight) greater than 800, more preferably in the range 880-1200, especially in the range 900-1100. Preferably component b) is of the Formula (I):

wherein R¹ is H or optionally substituted alkyl, preferably H or C_1-4-alkyl; and

each R³ independently is of the formula:

wherein n is from 3 to 8, preferably 4 to 8, more preferably 5; and R³ and R¹ are each independently hydrogen or C_1-4-alkyl, especially H or methyl.

As examples of compounds which can be used as or in component b) there may be mentioned highly propoxylated and ethoxylated 1,1,1-trimethylolpropane triacrylate or trimethacrylate. Compounds of this type are known and some are commercially available, for example SARTOMER products of Cray Valley Co. Limited, Newport, Wales and Sartomer Company supply such compounds under the product names SR-9021 and SR-9035.

One may use known urethane(meth)acrylates as component c) in compositions according to the invention and these can be prepared in a Known manner, for example by reacting a hydroxyl-terminated polyurethane with acrylic acid or methacrylic acid to give the corresponding urethane

(meth)acrylate, or by reacting an isocyanate-terminated prepolymer with hydroxyalkyl acrylates or methacrylates to give the

uretnane(meth)acrylate. Appropriate processes are disclosed in for example, published EP patent applications 114,982 and 133,908 The molecular weight of such acrylates is generally within the range from 40: to 13,333 preferably between 500 and 7,000.

Uretnane (meth)acrylates are also available commercially under the name NeoRad from Zeneca Resins, EBECRYL from UCB , Uvithane from Morten Thickol and SR 9504, SR 9600, SR 9610, SR 9620, SR 9631, SR 9643 and SR 9650 from the Sartomer Company.

It is preferaole to use a urethane (meth)acrylate or MW 531-7000 derived from an alipnatic starting material.

Di(meth)acrylates based on bisphenol A and bisphenol F which can be used as component d) include Disphenol A di(meth)acrylates and bisphenol F di(meth)acrylates and di(meth)acrylates of alkoxylated, preferably ethoxylated or propoxylated, bisphenol A or F. The

acrylates obtainable by reaction of bisphenol A or bisphenol F

diglycidyl ether with (meth)acrylic acid are also suitable. Monomeric or oligomeric di(meth)acrylates of this type are also known and some are available commercially, for example from the Sartomer Company under the product name SR-348 for ethoxylated bisphenol A dimethacrylate and under the product name SR-349 for ethoxylated bisphenol A diacrylate. It is preferable to use the di(meth)acrylates of bisphenol A or F and of ethoxylated bisphenol A or of ethoxylated bisphenol F as the component d).

Preferably component d) has a MW of 300-1000.

Any type of photoinitiator which forms free radicals when

irradiated suitably can be employed as the component e) in the mixtures according to the invention. Suitable classes of known photoinitiators are benzoins; benzoin ethers, for example benzoin methyl ether, ethyl ether and isopropyl ether, benzoin phenyl ether and benzoin acetate; acetophenones, e.g. acetophenone, 2,2-dimethoxyacetophenone and 1,1-dichloroacetophenone; benzil; benzil ketals, e.g. benzil dimethyl ketal and benzil diethyl ketal; anthraquinones, e.g. 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone and 2-amylanthraquinone; triphenylphosphine; benzoylphosphine oxides, e.g. 2,4,6-trimethylbenzoyldiphenylpnospine oxide (Lucinn TPO);

benzophenones, e.g. benzophenone and 4,4-bis-(N,N-dimethylamino)benzophenone; thioxanthones and xanthones; acridine derivatives;

phenazine derivatives; quinoxaline derivatives and 1-phenyl-1,2-propanedione-2-O-benzoyl oxime; 1-aminophenyl ketones and 1-hydroxyphenyl ketones, e.g. 1-hydroxycyclohexyl phenyl ketone, phenyl 1-hydroxyisopropyl ketone and 4-isopropylphenyl-1-hydroxyisoprcpyl ketone; all of which are known compounds.

Photoinitiators which are particularly suitable for use when the actinic radiation is from a He-Cd laser are acetophenones, e.g. 2,2-dialkoxybenzophenones, and α-hydroxyphenyl ketones, e.g. 1- hydroxycyclohexyl phenyl ketone and 2-hydroxyisopropyl phenyl ketone (=2-hydroxy-2,2-dimethylacetophenone).

A class or photoinitiators e) particularly suitable for argon ion lasers are benzil ketals, for example benzil dimethyl ketal, and especially an α-hydroxyphenyl ketone, benzil dimethyl ketal or 2,4,6- trimethylbenzoyldiphenylphosphine oxide.

Another class of suitable photoinitiators e) are the ionic dye- counter ion compounds which are capable of absorbing actinic radiation and producing free radicals which initiate the polymerisation of the components. The mixtures according to the invention containing ionic dye-ccunter ion compounds can be cured in a fairly variable manner in this way with visible light having a wavelength of 400-700nm. Ionic dye-ccunter ion compounds and their mode of action are known, for example from EP-A-0,223,587 and US Patents 4,751,102, 4,772,530 and 4,772,541. Examples of suitable ionic dye-counter ion compounds which may be mentioned are the anionic dye-iodonium ion complexes, the anionic dye-pyrylium ion complexes and especially, the cationic dye-borate anion compounds of the formula VI:

wherein X⁺ is a cationic dye and R₅, R₆, R₇ and R₈ are each independently alkyl, aryl, allyl, aralkyl, alkenyl or alkinyl group, an alicyclic group or a saturated or unsaturated heterocyclic group.

The photoinitiators are added in effective amounts, i.e. in amounts of about 0.1 to about 10 parts by weight, relative to the total amount of the components a) to e) mixture. If the mixtures according to the invention are used for stereolithographic processes in which laser radiation is used, it is preferred that the absorption capacity of the compositions is so adjusted by means of the type and concentration of the photoinitiator that the depth of curing at normal laser speed is approximately 0.1 to 2.5mm.

Compositions according to the invention can contain a plurality of photoinitiators which have a different radiation sensitivity at

different wavelengths. This achieves, for example, better utilisation of a UV/VIS light source which radiates emission lines of different wavelengths. It is advantageous in this case if the various

photoinitiators are so chosen and employed in such a concentration that a uniform optical absorption is produced in the case of the emission lines used.

As will be understood from the foregoing description and from the

Examples, the specified amounts of components a) to d) refer to the total number of parts by weight of each of the defined component types. For example a mixture 18 parts of an ethoxylated bisphenol A diacrylate and 18 parts of ethoxylated bisphenol A dimethacrylate constitute 36 parts in total and as such satisfy the definition for component d).

If desired one may add customary additives to the compositions, for example stabilisers, e.g. UV stabilisers, polymerisation inhibitors, mould release agents, wetting agents, flow control agents, infra-red absorbers, sensitisers, anti-sedimentation agents, surface-active agents, dyes, pigments and fillers.

Compositions according to the invention can be prepared in a known manner, for example by premixing individual components and subsequently mixing these premixes or by mixing all the components by means of customary devices, such as stirred vessels, in the absence of light and, if appropriate, at a slightly elevated temperature.

Liquid compositions according to the invention can be polymerised by irradiation with actinic light, for example, by means of electron or X-ray beams or UV or VIS light, e.g. by means of radiation within the wavelength range from 280 to 650nm. Laser radiation from HeCd, argon ions, or nitrogen ions and also metal vapour and NdYAG lasers of multiplied frequency are particularly suitable. It is known to those skilled in the art that the suitable photoinitiator must be selected and, if appropriate, sensitised for each light source selected.

The invention also relates to a process for polymerising liquid compositions according to the invention by irradiating them with actinic light.

Liquid compositions according to the invention preferably have a viscosity of below 1000 mPa.s, more preferably below 750 mPa.s, at 30°C. Compositions according to the invention have surprisingly low viscosity and this enables fast processing times in stereolithography.

The invention also relates to a process for the production of a three-dimensional solidified article from a liquid composition, preferably by stereolithography, characterised in that the liquid composition is as defined for the present invention. Preferably this entails (a) the surface of a layer of the liquid composition according to the invention being irradiated either as the whole surface or in a predetermined pattern, by means of a UV/VIS light source, so that a layer is solidified in a desired layer thickness in the irradiated areas,

(b) then a new layer of a composition according to the invention is formed on the solidified layer, and this is also irradiated either as the whole surface or in a predetermined pattern; and

(c) by repeating steps- (a) and (b) a three-dimensional article composed of several solidified layers adhering to one another is obtained

The number or times steps (a) and (b) are repeated depends on the thickness or the resultant solidified aayers and the size of the articles. Thus steps (a) and (b) could be repeated 10 times if each solidified layer was 1mm deep and the article 1cm high and 500 times if each solidified layer was 0.5mm deep and the article 25cm high

Preferably the solidified layers each independently have a depth of 0.1 to 1mm, more preferably 0.2 to 0.6mm, especially 0.25 to 0.4mm. The solidified layers do not need to all be of the same depth. Pepetition of steps (a) and (b) from 10 to 10,000, preferably 20 to 2,000 times, forms one aspect of the invention.

The process for forming a three-dimensional article preferably uses a stereolithography apparatus, for example the SLA 250 or 500 supplied by 3D-Systems or the Stereos 300, 400 and 600 supplied by EOS.

There is no particular limit on what the three dimensional article can be, for example one may use the process to form ornamental and industrial articles and models of plant and animal parts. Industrial articles include mechanical parts, especially those used in automobiles, and models and prototypes thereof. Animal parts include bones, organs, tissues and combinations thereof. Examples of bones include joints (e.g. ball and socket joints such as the hip and shoulder, hinge joints such as the knee and elbow) the skull, jaw, spine, ribs, collarbone, shoulder blade, humerus, radius, ulna, teeth, finger and hand bones, breast bone, femur, tibia and fibula. Examples of organs include the liver, heart, lungs, kidneys, bladder, brain, eyes, intestines, pancreas and reproductive organs. Examples of tissue include muscle and cartilage.

As desired the three dimensional article can be a model which is the same size, smaller or larger the original article. The low curl distortion and high rate of cure mean that such articles can be prepared quickly and accurately.

It is preferable to use a laser beam as the radiation source in this process.

The invention also provides three-dimensional solidified articles prepared by stereolithography using a liquid composition according to the present invention.

Compositions according to the invention may also be used as coating agents; clear and hard coatings can be obtained on wood, paper, metal, ceramics or other surfaces. The coating thickness can be varied between wide limits, for example from 1 micrometer to 1mm.

Relief images for printed circuits or printing plates can be produced direct from compositions according to the invention by irradiating the mixtures, for example by means of a computer-controlled laser team of suitable wavelength or using a photomask and a corresponding light source

It is preferable to use compositions according to the invention for the production of photopolymerised layers, particularly in the form or three-dimensional solidified articles built up from several

solidified layers adhering to one another.

The curl factor is determined on test specimens produced by stereolithographic processes, the deformation of a self-supporting part of the test specimen being determined by shrinkage. The curl factor is the ratio of the height of a deformed, fixed segment of the test specimen to the height of the non-deformed segment.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless stated otherwise.

The following abbreviations are used in the Examples:-

Examples 1 to 3

Liquid compositions according to the invention were prepared by stirring together at room temperature the number of parts by weight of components indicated in Table 1 below. After stirring for a few hours the homogenous mixtures were transferred into separate bottles for storage.

Viscosities were measured at 30-C on a Brookfieid viscometer RVTV- II using spindle 27 at 100 rpm and are shown in Table 2 below.

The viscosities are lower than those stated in the Examples of CA 2028541.

Additionally the compositions of Examples 1 to 3 were found to have low curl distortion when cured by stereolithography.

Examples 4 to 9

Further liquid compositions may be prepared having the formulations given in Table 3 below.

Examples 11 to 13

Further liquid compositions may be prepared having the formulations given in Table 4 below:

Claims

1. A liquid composition comprising:

a) 5 to 25 parts of a monomeric aliphatic or cycloaliphatic

di(meth)acrylate having a MW of not more than 800;

b) 2 to 20 parts of a monomeric poly(meth)acrylate having a

functionality of at least 3 and a MW of at least 610;

c) 12 to 40 parts of a urethane(meth)acrylate having a

functionality of 2 to 4 and a MW of 400 to 10,000;

d) 35 to 70 parts of a monomeric or oligomeric di (meth)acrylate based on bisphenol A or bisphenol F; and

e) 0.1 to 10 parts of a photoinitiator;

wherein all parts are by weight, the total number of parts of a) + b) does not exceed 30 and the total number of parts of a) + b) + c) + d) + e) add up to 100.

2. A liquid composition according to claim 1 which comprises or consists essentially of 6 to 22 parts of component a); 3 to 18 parts of component b); 15 to 38 parts of component c); 40 to 68 parts of component d); and 1 to 9 parts of component e); wherein all parts are by weight, the total number of parts of a) + b) does not exceed 30 and the total number of parts of a) + b) + c) + d) + e) add up to 100.

3. A liquid composition comprising:

a) 6 to 20 parts of a monomeric aliphatic or cycloaliphatic

di(meth)acrylate having a MW of not more than 800;

b) 3 to 15 parts of a monomeric poly(meth)acrylate having a

functionality of at least 3 and a MW of at least -610;

c) 16 to 35 parts of a urethane(meth)acrylate having a

functionality of 2 to 4 and a MW of 400 to 10,000;

d) 42 to 65 parts of a monomeric or oligomeric di (meth) acrylate based en bisphenol A or bisphenol F; and

e) 2 to 3 parts of a photoinitiator;

4. A liquid composition according to any one of the preceding claims wherein the monomeric aliphatic or cycloaliphatic di(meth)acrylate having a MW of not more than 800 is a di(meth)acrylate ester of an aliphatic or cycloaliphatic diol.

5. A liquid composition according to any one of the preceding claims wherein the monomeric poly(meth)acrylate having a functionality of at least 3 and MW of at least 510 is of the Formula (I) :

wherein R¹ is H or optionally substituted alkyl, preferably H or C alkyl; and

each R³ independently is of the formula:

wherein n is from 3 to 8 , preferably 4 to 8, more preferably 5; and R³ and R⁴ are each independently hydrogen or C_1-4 -alkyl, especially H or methyl.

6. A liquid composition according to any one of the preceding claims wherein the urethane(meth)acrylate having a functionality of 2 to 4 and a MW of 400 to 10,000 is a urethane meth (acrylate) of MW 500 to 7000 derived from an aliphatic starting material.

7. A liquid composition according to any one of the preceding claims wherein the monomeric or oligomeric di(meth)acrylate based on bisphenol A or bisphenol F is a di(meth)acrylate of alkoxyiated bisphenol A or F.

8. A liquid composition according to any one of tine preceding claims having a viscosity below 1000 mPa.s at 30C.

9. A process for the production of a three-dimensional solidified article from a liquid composition by stereolithography, characterised in that the liquid composition is as defined in any one of claims 1 to 8.

10. A process for the production of a three-dimensional solidified article wherein:

(a) the surface of a layer of a liquid composition according to any one of claims 1 to 8 is irradiated either as a whole surface or in a predetermined pattern, by means of an ultraviolet or visible light source such that a layer is solidified in a desired layer thickness in the irradiated areas;

(b) then a new layer of the composition is formed on the solidified layer, and this is also irradiated either as a whole surface or in a predetermined pattern; and

(c) by repeating steps (a) and (b) a three-dimensional article composed of several solidified layers adhered to one another is obtained.

11. A three-dimensional solidified article prepared by

stereolithography using a liquid composition according to any one of claims 1 to 8.

12. Use of a liquid composition according to any one of claims 1 to 8 for the preparation of a three-dimensional solidified article.