AU1553397A

AU1553397A - Liquid composite moulding process

Info

Publication number: AU1553397A
Application number: AU15533/97A
Authority: AU
Inventors: Riyadh Najeeb Alaka; James Rylance Maddison
Original assignee: Kobe Steel Europe Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1996-01-30
Filing date: 1997-01-30
Publication date: 1997-08-22
Also published as: GB9601783D0; WO1997027993A1; JP2000503922A

Description

LIQUID COMPOSITE MOULDING PROCESS

This invention relates to a liquid composite moulding (LCM) process and more particularly to the use of organometallic coupling agents in LCM.

An LCM process is one in which a liquid resin (usually a thermosetting resin), or liquid reaction components for the resin, is injected into a mould and allowed to cure in the mould. Following curing, the resulting moulded article is removed from the mould. LCM comprises a number of techniques, such as:

resin transfer moulding (RTM) vacuum assisted resin injection (VARI) reinforced reaction injection moulding (R-RIM) structural reaction injection moulding (S-RIM)

In the case of RTM and S-RIM, various types of additives are added to the resin and mixed, prior to the addition of powder type fillers. The resin mixture and any additional reactants (such as hardeners or accelerators) are then mixed and injected into a mould loaded with fibrous reinforcements. Once the resin is set, the mould is opened and the moulded article removed. In the case of VARI, vacuum is used instead of pressure to introduce the resin mixture into the mould. RTM and VARI can be combined together, whereby both pressure and vacuum are used concurrently to fill the mould. In the case of R-RIM, the reinforcements, if added, are placed in one of the reactants with the lowest viscosity, and injected into an empty mould once the other reactants are mixed in. The resins used are any liquid mouldable resins. The fillers most commonly used are calcium carbonate or alumina trihydrate (ATH) powders. The reinforcement is usually mats made from continuous or discontinuous fibres, particularly glass fibres. Such techniques are used in a variety of applications worldwide, in a number of fields such as automotive, transport and industrial. Coupling agents are chemicals which have been known to promote adhesion between mostly (but not limited to) mineral or inorganic phases and organic phases, typically in mineral filled and or glass reinforced polymer systems. More contributions to the understanding of the required functionalities, thus possible chemical structures of the coupling agent can be found by exploring the most significant reaction processes which, for silane based coupling agents are:

Hydrolysis

R'-Si-(OR)₃ + excess H₂O → R'Si(OH)₃ + 3ROH where R must be a hydrolysable organic group (hence functional) and the R'-Si bond is preferably non-hydrolysable but stable throughout this reaction.

Condensation

R'-Si(OH)₃ + Organic phase → R'Si(OH)₂-Organic Phase or inorganic phase surface

+H₂O

Both reactions can occur concurrently. Other reactions can occur in use eg. alcoholysis or reactions with other nucleophiles. All these reactions are reversible and many are at equilibrium with substantial concentrations of both products and reactants present under typical conditions of use.

For Organometallic Coupling agents eg. Al, Ti, Zr, or Zr-Al based coupling agents: -

the mechanisms are different where the organometallic coupling agent reacts with the substrate surface protons of the inorganic phase, resulting in the formation of matrix-compatible/reactive organic layers on the inorganic surface by one or more of the following reaction categories :- alcoholysis (solvolysis), surface chelation, co-ordination exchange, co-ordination salt formation, polymer ligand exchange catalysis and organic ligand interaction. However, the general mechanisms covering all known species to date are as follows: -

1 a) Inorganic phase (IP) + Coupling Agent (CA) → CA-IP

1 b) Organic Matrix (OM) + Coupling Agent (CA) → CA-OM

2 a) CA-IP + OM → OM-CA-IP (bridge concept) 2 b) OM-CA + IP → OM-CA-IP (bridge concept)

OM-CA-IP + n {IP/OM/CA} → n {-OM-CA-IP-}-

Solvation of Compatible phase chain. Where n can be any number.

The use of coupling agents in general for improving mechanical properties of composite materials is known, for example from the following references:

Salvatore J. Monte, "Titanate, Zirconate and aluminate coupling agents", Ken- React reference manual, Kenrich Petrochemicals Inc., Second Revised Edition, Summer 1993.

Harry S. Katz and John V. Milewski, "Handbook of Fillers of Plastics", Van Nostrand Reinhold, New York, 1987.

This is attributed to better wet-out of the mainly inorganic phases (fillers and fibres) by the organic phase (resin) and better bond adhesion between them. Coupling agents can either be coated onto the inorganic phases or added to the organic phase prior to mixing any other constituents. The coupling agents can be organometallic compounds, in particular titanates, zirconates, aluminates and zircoaluminates. Organometallic coupling agents are also known to improve the rheological properties of composite materials during processing. For example, titanate-based coupling agents were found to reduce the mixing time of the constituents used in manufacturing Bulk Moulding Compounds (BMC), see Katz et al referred to above, Chapter 4. Titanates and zircoaluminates have also been reported to be more effective in reducing viscosity and flow activation energy when compared with silicon-based coupling agents (silanes) in unsaturated polyester, as described in the following references:

Wen Dijiang, Lu Feng and Hou Xiaofeng "Interfacial Effects of Coupling Agents on the Rheological Properties of GF/UP Systems", Proc. Int. Symp. Fib. Reinf. Plast./Comp. Mat. , Nanjing, 15-18th April 1988, paper 21, pp627.

Lawrence B. Cohen, "Zircoaluminate Metallo Organic Coupling Agents: A New Dimension in Composite Materials" , NATEC'83 Discovering New Frontiers Through Imagination; Proc. Nat. Tech. Conf., Detroit, Mich, Sept. 20th-22nd, 1983, pp24-6.

This is attributed to better filler dispersion and possibly to the formation of flexible chain structure between organometallic coupling agent and the inorganic phases present in the resin. However, no use of organometallic coupling agents in LCM processes has been disclosed.

A particular problem which we have identified in LCM processes is the fact that the reinforcement in the mould acts as a filter. This causes the dispersion of filler in the resin to become non-uniform, with deterioration of mechanical, fire, smoke and toxicity (FST) and electrical properties. Additives are currently used in LCM processes for filler dispersion and for wetting, e.g. air release agents which attempt to eliminate pockets of air in the reinforcements. An example of such additives is silicon-based compounds, e.g. polyester modified ethylalkylpolysiloxane copolymer which is available from BYK-Chemie GmbH, Germany. However, such additives do not satisfactorily solve the problem of filler filtration.

Moulding techniques used in RTM where the filler filled resin mixture is aided to flow more readily throughout the mould are described in WO 89/00495. This technique was referred to in the literature as "Network Injection Moulding" (NIM). The moulding contains one or more galleries in its core or/and fibre skin with resin being injected into the gallery or galleries and transmitted to all portions of the skin. This technique is being used in the production of composite articles such as manhole covers, see EP-A-0 147 050.

Another technique invented by See ann described in US-A-5 052 906 is called Seemann Composite Resin Infusion Moulding Process (SCRIMP). In SCRIMP, the resin is introduced into a chamber below the fibre preform and a vacuum is then applied upon the chamber which will result in the resin flowing through the fibre preform and filling the mould. The technique is being used in the manufacture of large composite articles such as boats and rail cars. Nevertheless, filler filtration is expected as the resin mixture travels through the fibre preform.

According to the present invention, there is provided a liquid composite moulding process, in which a liquid mouldable resin, or reaction components therefor, is injected into a mould, allowed to cure in the mould, and the resulting moulded article removed from the mould, characterised in that an organometallic coupling agent is in contact with the liquid resin or reaction components during injection thereof into the mould.

The invention also relates to the use of an organometallic coupling agent in liquid composite moulding for reducing filler filtration.

Thus, according to the invention, organometallic coupling agents are used as a means of reducing filler filtration and as a flow modifier in LCM generally, and in particular in RTM, VARI, R-RIM and S-RIM. Furthermore, the organometallic coupling agents improve composite surface finish by reducing surface roughness and improve mechanical properties by reducing fibre mat deformation (fibre wash) which tends to occur during mould fill. The organometallic coupling agents represent a significant improvement over silicon- based additives. The use of the organometallic coupling agents leads to significantly improved LCM cycle time, product quality and process economics.

The invention is preferably applicable to cases where fibrous reinforcements are present in the mould and are permeated by the liquid resin or reaction components. Suitable fibres include glass fibre, carbon fibre and aramid fibre. The invention permits a high volume fraction of fibre (e.g. up to 60%) and long fibres (e.g. 200 microns or greater) as well as continuous fibres to be used. The fibres used can be random, woven or unidirectional in a variety of styles. In the case of R-RIM, shorter fibrous reinforcements are used and these are dispersed in one of the reaction components.

The resins which can be used include liquid mouldable resin, such as epoxy, polyesters, vinylesters, acrylics, poiyurethanes, polyureas and phenolics. In the case of RIM processes, the reaction components which together form the liquid thermosetting resin (e.g. an epoxy resin and a curing agent) are mixed by impingement of separate streams, immediately before injection into the mould.

The resins contain filler, in particular particulate fillers such as calcium carbonate, alumina trihydrate, talc, quartz, titanium oxide, carbon black or glass spheres. The organometallic coupling agent can be added to the liquid thermosetting resin or to one or more of the reaction components. It can also be used as a coating on the fibrous reinforcements and/or on filler particles. More than one coupling agent can be used simultaneously. The proportion of organometallic coupling agent which is present is generally up to 2.0 phf, preferably around 0.2-2.0 phf (parts per hundred of filler).

The organometallic coupling agents which can be used are known compounds, such as those disclosed in the Monte and Katz et al references mentioned above. Particularly preferred organometallic coupling agents are compounds of the following general types:

Monoalkoxy and Neoalkoxy titanates (eg. LICA 38: neopentyl(diallyl)oxy, tri(dioctyl)pyro-phosphato titanate) .

Chelate aluminates (eg. KA301 : diisobutyl(oleyl)aceto acetyl aluminate).

Quat titanates and Zirconates (eg. KR238A/M: acrylate functional amine adduct of KR238S / methacrylate functional amine adduct of KR238S).

Coordinate titanates and Zirconates (eg. KR55: tetra (2,2 diallyoxymethyl)butyl, di(ditridecyl)phosphito titanate).

Cycloheteroatom titanates and zirconates (eg. KROPPR : cyclo(dioctyl)pyrophosphato dioctyl titanate).

Neoalkoxy zirconates (eg. NZ38: zirconium IV 2,2(bis-2-propenolatomethyl) butanolato , tri s(diocty l)pyrophosphato-0) .

Chelate titanates (eg. KR238S: di(dioctyl)pyrophosphato ethylene titanate). General formulae for some of the above types are given on page 78 of the Katz et al reference. Other suitable coupling agents are listed in the following:

isopropyl triisostearoyl titanate; isopropyl dimethacryl isostearoyl titanate; isopropyl tri(dodecyl)benzenesulfonyl titanate; isopropyl tri(dioctyl)phosphato titanate; isopropyl (4-amino)benzenesulfonyl di(dodecyl)benzenesulfonyl titanate; alkoxy trimethacryl titanate; isopropyl tri(dioctyl)pyrophosphato titanate; alkoxy triacryl titanate; isopropyl tri(N-ethylenediamino)ethyl titanate; di(cumyl)phenyl oxoethylene titanate; di(dioctyl)pyrophosphate oxoethylene titanate; dimethacryl, oxoethylene titanate; di(butyl, methyl)pyrophosphato, oxoethylene di(dioctyl)phosphato titanate; di(dioctyl)phosphato, ethylene titanate; di(butyl, methyl)pyrophosphato, ethylene titanate; cycloneopentyl, cyclo(dimethylamino- ethyl) pyrophosphato zirconate, di mesyl salt; isopropyl diisostearoyl methacryl titanate; titanium di(dioctyl)phosphate oxyacetate titanate; titanium di(cumyl)phenylate oxyacetate titanate; di(dioctyl)pyrophosphato ethylene titnanate; di(butyl, methyl)pyrophosphato, ethylene titanate; tetraisopropyl di(dioctyl)phosphito titanate; tetra octyl di(ditridecyl)phosphito titanate; tetra (2,2- diallyoxymethyl) di(ditridecyl) phosphito zirconate; neoalkoxy, tri neodecanoyl titanate; neoalkoxy, tri(dodecyl)benzene sulfonyl titanate; neoalkoxy, tri(dioctyl)phosphato titanate; neoalkoxy tri(dioctyl)pyrophosphato titanate; neoalkoxy, tri(N-ethylene diamino) ethyl titanate; neoalkoxy, tri(m-amino)phenyl titanate; neoalkoxy trihydroxy caproyl titanate; neoalkoxy, tri neodecanoyl zirconate; neoalkoxy, tri(docecyl)benzene sulfonyl zirconate; neoalkoxy, tri(dioctyl)phosphato zirconate; neoalkoxy, tri(N-ethylene diamino) ethyl zirconate; neoalkoxy , tri(m-amino)phenyl zirconate; 2 ,2(bis-2- propenolatomethyl)butanolato, trineodecanoyl titanate; 2,2(bis-2- propenolatomethyl) butanolato, dodecylbenzenesulfonyl titanate; 2,2(bis-2- propenolatomethyl) butanolato, tri(dioctylphosphato) titanate; 2,2(bis-2- propenolatomethyl) butanolato, tri(dioctylpyrophosphato) titanate; 2,2(bis-2- propenolatomethyl) butanolato, tri(N ethylaminoethylamino) titanate; 2,2(bis-2- propenolatomethyl) butanolato, tri(m-amino)-phenyl titanate; 2,2(bis-2- propenolatomethyl) butanolato, trineodecanoyl zirconate; 2,2(bis-2- propenolatomethyl) butanolato, dodecylbenzenesulfonyl zirconate; 2,2(bis-2- propenolatomethyl) butanolato, tri(dioctylphosphato) zirconate; 2,2(bis-2- propenolatomethyl) butanolato, tri(dioctylpyrophosphato) zirconate; 2,2(bis-2- propenolatomethyl) butanolato, tri(N ethylaminoethylamino) zirconate; 2,2(bis-2- propenolatomethyl) butanolato, tri(m-amino)-phenyl zirconate; dicyclo(dioctyl)pyrophosphato, titanate; cyclo(dioctyl)pyrophosphato dioctyl zirconate; cyclo[dineopentyl(dialIyl)]pyrophosphato dineopentyl(diallyl) zirconate; neopentyl(diallyl)oxy, trimethacryl zirconate; neopentyl(diallyl)oxy, triacryl zirconate, dineopentyl(diallyl)oxy, diparamino benzoyl zirconate; dineopentyl(diallyl)oxy, di(3-mercapto) propionic zirconate.

The invention thus relates to the addition of organometallic coupling agents, such as titanate, zirconates, aluminates and their combinations such as zircoaluminates, to filler-loaded liquid mouldable resins, e.g. thermosetting resins such as epoxy, polyester, acrylics, but not excluding others, used in LCM in order to reduce mould fill time, reduce filler filtration, reduce surface roughness, increase mechanical performance and reduce overall product cost. The ability of the organometallic coupling agents to improve the flow characteristics of the resin mixture during LCM is not necessarily due to a viscosity reduction effect. We have found that this is the case, as the mixing ratios of organometallic coupling agents are lower than those for silicon-based additives (on average 1.0 phf compared with 2.0 phf, respectively). The effect of the invention is more based on the capability of the organometallic coupling agents to act as effective dispersing agents, reducing filler filtration by the reinforcements. The invention has the following advantages:

(a) a reduction in mould fill time by up to a half in comparison with silicon based additives for a given mould, set of operating conditions and materials. The moulding cycle time is thus reduced and the product and process economics greatly improved.

(b) twice as much filler content can be added to the resin and moulded successfully in comparison with silicon-based additives for a given mould, set of operating conditions and materials. This contributes to lower shrinkage, better surface finish and lower materials cost.

(c) filler filtration is substantially reduced relative to silicon-based additives for a given mould, set of operating conditions and materials. This results in improved product performance, such as higher mechanical and lower fire, smoke and toxicity (FST) values.

(d) surface roughness is reduced relative to silicon-based additives for a given mould, set of operating conditions and materials. This improves surface finish and facilitates painting after moulding.

(e) improved mechanical properties relative to silicon-based additives as a result of very reduced fibre mat deformation and wash during the injection of the resin mixture into the mould. In structural applications, this can be a most important factor, since any distortion of unidirectional fibre reinforcements can cause rejection of the moulding.

(f) reduced resin injection pressure for a given mould, set of operating conditions and materials. Consequently, it will be possible to use low pressure matched metal moulds and low pressure presses.

(g) pigment dispersion and colour homogeneity are improved relative to silicon - based additives.

The invention is illustrated by the following Examples. The coupling agents used are described in the Monte reference identified above.

Example 1

KR238 A or M was mixed (0.5 phf) with unsaturated polyester resin (Norpol 4010) and two levels of CaCO3 (60 and 120 phr). The mixtures were moulded by RTM using Woven Roving (W/R) glass mat (566 g/m²) and surface veil giving fibre volume content of 38% . Two mould temperatures were used, 50 and 60°C, and 3.8 bar resin injection pressure. The same again was carried out using BYK-W995 (1.25 phf), a silicon-based additive, instead of KR238 A or M.

Luperox GZN at 3 phr (Benzoyl peroxide hardener)

Co (1 %) in styrene at 3 phr (Stypol Accelerator II, cobalt octoate 1 % in styrene)

Agent Injection Temperature Filler Filler Surface time(s) (C) Content Filtration roughness (phr) (μm)

KR238A 112 50 60 LOW 9.0

W995 152 50 60 HIGH 14.0

KR238M 79 60 60 LOW 9.0

W995 137 60 60 HIGH 13.0

KR238A 152 50 120 LOW 0.1

W995 323 50 120 HIGH 2.0

KR238M 60 60 120 LOW 1.5

W995 249 60 120 HIGH 1.2 Surface roughness Expected surface

(μm) finish quality

_< 1 V.Good

2-3 good

4-10 average

_>_13 poor

Surface roughness was measured by laser profilemetry

Example 2

KR238 A was mixed (0.5 phf) with unsaturated polyester (Norpol 4010) and 60 phr CaCO3. The resin mixture was injected into a mould set at 50°C temperature and loaded with continuous filament mat (CFM) fibre reinforcement (450g/m²) and surface veil giving a fibre content of 38%. The injection pressure was 3.8 bar. The same was repeated with 1.25 phf of BYK-W995 instead of KR238A.

Luperox GZN at 3 phr Co (1 %) in styrene at 3 phr

Injection Filler Surface

Agent time(s) Filtration roughness (μm)

KR238A 22 low 9

W995 30 average 14

Example 3

KR238S was mixed (1.25 phf) with modified acrylic resin (Modar 836S) and 60 phr of a mixture of FST filler powders (mainly alumina trihydrate). The resin mixture was moulded by RTM using a non crimp triaxial (0/+45/-45) glass fabric (Cotech ETLX- 1169-3131) of 1169 g/m² weight giving fibre volume content of 40% . Mould temperature was 40°C and the resin injection pressure was 4 bar. The same again was repeated with BYK-W995 (1.25 phf) instead of KR238S.

BPO (40%) at 3.75 phr (Benzoyl peroxide hardener) DMA at 1 phr (Dimethyl aniline accelerator)

Injection Filler Surface

Agent time(s) filtration Finish

KR238S 400 low good/glossy

W995 510 average average *

* Significant fibre mat deformation

Example 4

A number of organometallic coupling agents (given below) were individually mixed (1.25 phf) with polyester resin (Norpol 4010) and 50 phr CaCO3 filler powder. The resin mixtures were injected into a mould at 3.8 bar pressure, which contained W/R glass fibre reinforcement and surface veil (36% fibre volume). The mould temperature was set at 50°C. The same filler, reinforcement and moulding conditions were employed again using BYK-W995 (1.25 phf) instead of organometallic coupling agents. Luperox GZN at 3 phr

Co (1 %) in styrene at 3 phr

Injection Filler Surface

Agent time(s) filtration Finish

KA301 95 low good/glossy

NZ38 41 low good/ mat

LICA38 44 average poor *

KR55 69 low average

KR238A 50 low V. good/glossy

W995 120 high average/glossy (pin holes)

* LICA38 is known to slow down the cross linking reaction of polyester hence a higher Co% (eg. 6%) could be needed to accelerate the reaction and achieve a complete cure.

Example 5

As in Example 4 but using modified acrylic resin (Modar 836S) instead of polyester resin, 50 phr FST filler powders instead of 50 phr CaCO₃ and BYK- W996 instead of BYK-W995.

BPO (40%) at 3.75 phr DMA at 1 phr

Injection Filler Surface

Agent time(s) filtration Finish

KA301 44 low V. good/high gloss

NZ38 48 low V. good/high gloss

LICA38 44 low good/glossy

KR55 70 average poor/incompatible

W996 50 high V.poor Example 6

A number of organometallic coupling agents (given below) were individually mixed (1.25 phf) with epoxy resin (Bis-F) and 50phr CaCO3 filler powder. The resin mixtures were injected into a mould at 3.8 bar pressure which contained W/R glass fibre reinforcement and surface veil (36% fibre content). The mould temperature was set at 60°C. The same filler, reinforcement and moulding conditions were employed again using BYK-A530 (1.25 phf) and BYK-S732 (1.25phf) instead of organometallic coupling agents.

Amine curing agent at 21 phr post cure at 125°C for 60 minutes

Injection Filler Surface

Agent time(s) filtration Finish

NZ38 52 average good/glossy

KA301 40 low V. good/high gloss

KR55 80 low V. good/glossy

A530 120 high poor/surface porosity

*S732 35 high poor/reduced surface porosity

* High filler filtration and poor surface finish can lead to such mouldings being rejected even though the injection time is short.

Claims

CLAIMS:

1. A liquid composite moulding process, in which a liquid mouldable resin, or reaction components therefor, is injected into a mould, allowed to cure in the mould, and the resulting moulded article removed from the mould, characterised in that an organometallic coupling agent is present during injection of the liquid resin or reaction components into the mould.

2. A process according to claim 1 , in which a fibrous reinforcement is present in the mould and is permeated by the liquid resin or reaction components.

3. A process according to claim 1 , in which fibrous reinforcements are present in the liquid resin or a reaction component therefor.

4. A process according to claim 2 or 3, in which the fibrous reinforcements comprise glass fibre, carbon fibre or aramid fibre.

5. A process according to any of claims 1 to 4, in which the resin is an epoxy, polyester or acrylic resin.

6. A process according to any of claims 1 to 5, in which the organometallic coupling agent is a titanate, zirconate, aluminate or zircoaluminate.

7. A process according to claim 6, in which the organometallic coupling agent corresponds to one of the following general types:

Monoalkoxy and Neoalkoxy titanates, Chelate aluminates, Quat titanates and Zirconates, Coordinate titanates and Zirconates, Cycloheteroatom titanates and zirconates, Neoalkoxy zirconates, Chelate titanates.

8. Use of an organometallic coupling agent in a liquid composite moulding process for reducing filler filtration.