NL1007434C2 - Nano-composite material - Google Patents

Abstract

Use of a surfactant having an ammonium, pyridinium, sulfonium or phosphonium header group with two apolar organic pendant groups to modify a clay with a layered structure and a cation exchange capacity of 30-250 meq/100 g to render the clay compatible for incorporation into a polyolefin matrix. A nanocomposite material based on a clay with a layered structure and a cation exchange capacity of 30-250 (50-200) milliequivalents/100 g, a polyolefin matrix and a surfactant having an ammonium-, pyridinium-, sulfonium- or phosphonium-group as header group to which are attached two apolar, organic pendant groups. Independent claims are also included for: (A) the use of a surfactant as above to modify a clay with a layered structure and a cation exchange capacity of 30-250 meq/g to render it suitable for incorporation into a polyolefin matrix; and (B) modified clays per se.

Description

VO 1276

Title: Nanocomposite material

The invention relates to a nanocomposite material based on clay and a polyolefin, to a method for the preparation thereof and to a modified clay.

5 Polyolefins are materials used for a very wide range of applications. The main examples range from foils and packaging to molded parts, such as trays, toys and utensils. Polyolefins have very suitable properties for these applications. In addition, they are readily available and economically very attractive to use. An additional advantage of using polyolefins is that they do not have unacceptable adverse effects on the environment in waste processing. Namely, the combustion of polyolefins mainly produces carbon dioxide and water.

However, there are several properties of polyolefins that can be improved. This includes in particular the mechanical strength, which includes inter alia the tensile strength and the stiffness, and the permeability of the materials. Especially when polyolefins are used as packaging material, it is important that their air and water vapor permeabilities are as small as possible. Thus, the shelf life of food products packed in a package made of a polyolefin appears to be directly dependent on the permeability of the packaging material. In practice, these properties are not always sufficient.

For that reason, for example, an aluminum coating 1 00743 4-2 is often applied to the inside of food packaging which must be very well protected against moisture and / or oxygen, such as chips and the like. It will be clear that the application of such coatings is undesirable for technical, economic and environmental reasons.

It is now known that various properties of polymers, including in particular mechanical strength and heat resistance, can be improved by incorporating a clay into a matrix of the polymeric material. However, a great difficulty in incorporating a clay into a polymeric matrix lies in the strongly different nature of the materials. The polymeric material of the matrix is a generally non-polar, organic material, while the clay is a much more polar, inorganic material. This difference makes it difficult to mix the materials together; they are intrinsically immiscible.

In order to obtain a homogeneous mixing of a clay and a polymeric matrix, it has been proposed to use various so-called 'compatibilizers'. These compatibilizers must separate the platelets of which the clay material consists so that polymer material can intervene and a homogeneous mixing is obtained. Choosing the right compatibilizer is of great importance.

In U.S. Pat. Nos. 4,889,885 and 4,810,734 it has been proposed to first swell the clay under the influence of a swelling agent and then add monomeric material and polymerize that material in the presence of the clay. A surfactant is used as the swelling agent, the cationic head group of which is exchanged with cations between the crystalline layers of the clay. The swelling agent tails should have a functional group that can interact with the monomeric material to form the polymers between the layers of the clay. The polymers described are resins such as polyamide resins and rubbery materials.

1 007434- * 3

European patent application 0 747 322 describes that in order to homogeneously disperse a clay in a rubber material, a two-component compatibilizer is required. The first is a so-called oniumion 5 with two tails. This is understood to mean a surfactant with a head group formed by an ammonium, pyridinium, sulfonium or phosphonium group and one or more, in this case two, non-polar tails. The second component is formed by one or more guest molecules, also 10 surfactants, necessary to break through the layer structure of the clay, so that it can be mixed homogeneously with the rubber material.

It is an object of the invention to improve the properties of a polyolefin material by including a clay in it. Because polyolefins are pre-eminently very non-polar materials, they are very difficult to mix with a mineral, highly polar material such as clay. The intrinsic immiscibility of a clay and a polyolefin matrix is very high.

Surprisingly, it has now been found that a clay and a polyolefin matrix are excellent at mixing when an onium ion with two non-polar tails is used as a compatibilizer. The use of additional guest molecules does not appear to be necessary in this case.

The invention therefore relates to a nanocomposite material based on a clay with a layered structure and a cation exchange capacity of 30 to 250 milliequivalents per 100 grams, a polyolefin matrix and a surfactant, which surfactant is a head group formed by an ammonium, pyridinium, sulfonium or phosphonium group, to which two nonpolar, organic tails are attached.

A nanocomposite material according to the invention appears to have very good properties. In particular, the mechanical strength, including tensile strength, stiffness and impact strength, and permeability to liquids, such as water and solvents, and to gases, such as water vapor and oxygen, are greatly improved compared to polyolefin materials that are not modified with a clay. Furthermore, a nanocomposite material according to the invention has been found to have a high heat resistance. In addition, a number of desirable properties of the polyolefin material, such as low electrical conductivity, are retained. For example, it has been found that the presence of the clay in the polyolefin material does not adversely affect the processability of the material in waste processing.

As stated, a nanocomposite material according to the invention is based on a clay with a layered structure. The clay can be natural or synthetic in nature. The clay preferably has a large contact surface.

Extremely suitable are clays based on layered silicates, such as layered phyllosilicate which is composed of magnesium and / or aluminum silicate layers 20, each about 7-12 A thick. Especially preferred are smectite-like clay minerals such as montmorillonite, saponite, hectorite, fluorhectorite, beidellite, nontronite, vermiculite, halloysite and stevensite. These materials impart very favorable mechanical properties and high heat resistance to a nanocomposite material.

The clay to be used has, as mentioned, a cation exchange capacity of 30 to 250 milliequivalents per 100 grams. When that capacity is greater than the above upper limit, it proves difficult to finely disperse the clay at the molecular level due to the strong mutual interaction of the clay layers. When the cation exchange capacity is lower than said lower limit, the clay proves difficult to modify, because the interaction with the onium ion is small. Preferably, a clay with a cation exchange capacity of 50 to 200 milliequivalents per 100 grams is used.

The polyolefin matrix present in a nanocomposite material according to the invention can be formed by any desired polyolefin material. Both homopolymers and copolymers can serve as a polyolefin matrix. The copolymers can contain various monomeric olefins. Copolymers can also be used which contain up to 40% by weight, preferably 15% by weight, based on the weight of the copolymer of non-olefin monomers.

Preferably, the polyolefin matrix is selected from the group consisting of polyethylene and polypropylene. Polyethylene is particularly preferably used as a polyolefin matrix. It has been found that the properties of polyethylene become extremely beneficial due to the presence of a clay incorporated therein according to the invention.

In order to be able to incorporate a clay into a polyolefin matrix in a nanocomposite material according to the invention, the presence of an onium ion with two tails is required. In the context of the invention, a two-tailed onium ion is understood to mean a surfactant, which surfactant comprises a head group formed by an ammonium, pyridinium, sulfonium or phosphonium group to which two non-polar tails are attached. The two non-polar tails attached to the head group of the onium ions are preferably carbon chains, such as alkyl chains. It has been found that in particular an onium ion with an ammonium head group is suitable for incorporating a clay in a polyolefin matrix.

Of the group of surfactants with an ammonium head group, according to the invention, a particular preference is given to those surfactants which satisfy the formula (I): 3 X '(I), wherein 1007434-6 - Rx and R2 independently of one another hydrogen or a methyl group, - R 3 is an alkyl group of 1, preferably 4 to 20, particularly preferably 8 to 18, carbon atoms, 5 - R 4 is an alkyl group of 6 to 20 carbon atoms or a phenylalkyl group comprising an alkyl group of 8 to 18 carbon atoms X is a counterion selected from the group of halides, sulfates and phosphates. Preferably X is' Cl 'or Br'.

By using a surfactant complying with formula (I) as a compatibilizer for mixing a clay with a polyolefin matrix, a particularly finely divided, homogeneous dispersion with excellent properties is obtained.

In a nanocomposite material according to the invention, the weight ratio of the amount of onium ion to the amount of clay is preferably between 0.01: 1 and 100: 1, particularly preferably between 0.05: 1 and 6: 1. The weight ratio of the amount of clay to the amount of polyolefin matrix is preferably between 1: 200 and 2: 1, particularly preferably between 1:50 and 1.2: 1.

The invention further relates to a process for the preparation of a nanocomposite material as described above. It should be noted that it is hereby possible to first combine the clay and the onium ion or first to combine the polyolefin matrix and the onium ion, and only then add the required third component. Furthermore, it is possible to combine all three of the necessary components, namely clay, polyolefin matrix and onium ion, at the same time.

However, it is preferred to first modify the clay with an onium ion of the nature described above. The invention therefore also relates to a modified clay suitable for preparing a nanocomposite material as described above, based on a clay with a layered structure and a 10074 34 · 7 cation exchange capacity of 30 to 250 milliequivalents per 100 grams, which clay is modified with an onium ion with two non-polar, organic tails. This modified clay can then be suitably mixed with a polyolefin matrix.

In the preparation of a nanocomposite material of the invention, in any of the aforementioned pooling sequences, it is preferable to pre-grind or pulverize the clay. Such a pretreatment of the clay results in a simpler and better mixing of the various components.

Bringing together the constituents of a nanocomposite material according to the invention can be carried out in any suitable manner, provided that it provides good mixing. Examples of ways of bringing the ingredients together include long-term stirring at elevated temperature and extrusion.

Suitable mixing conditions depend on the nature of the selected ingredients and can be easily determined by those skilled in the art. For example, both stirring and extrusion can be carried out at a temperature between 140 and 190 ° C. For example, an extruder with a double screw can be used for the extrusion.

The nanocomposite materials of the invention are particularly suitable for use in a wide variety of applications. The materials have excellent workability and can be formed in 30 conventional molding steps, such as injection molding and extrusion processes. Shaped articles of all kinds can be made from the present nanocomposite material. Examples include any application for which the polyolefin matrix material is suitable. As preferred applications, packaging materials 1007434-8, such as foils, and construction materials can be mentioned.

The invention will now be further elucidated by means of the following example.

5

EXAMPLE

A smearic clay mineral (1 g) with an ion exchange capacity of 135 mequ / 100 g was dissolved in 80 ml of water, heated to 80 ° C and ions exchanged with 1.28 g of dioctadecyl dimethyl ammonium bromide, as a solution in 50 ml of water. The resulting material was washed with water, lyophilized and characterized by X-ray diffraction. It was found that a complete ion exchange of the sodium ions of the clay with the organic cations had taken place (a change in "d-spacing" from 12.4 A to 38 A).

Co-extrusion of the obtained material and an HDPE homopolymer with an Mw = 35,000 resulted in a composite material with homogeneously dispersed exfoliated platelets. This was demonstrated with X-ray diffraction, TEM and SEM.

Mechanical tests (DIN 53455) showed that the tensile modulus of the composite material was about 50% greater than that of the HDPE starting material, while the tensile strengths were about the same. Furthermore, the degradation temperature of the composite material was found to be about 100 ° C higher than that of the starting HDPE.

10074 34 · »

Claims (13)

1. Nanocomposite material based on a clay with a layered structure and a cation exchange capacity of 30 to 250 milliequivalents per 100 grams, a polyolefin matrix and a surfactant, which surfactant is a head group formed by an ammonium, pyridinium, sulfonium or phosphonium group to which two non-polar, organic tails are attached. Nanocomposite material according to claim 1, wherein the clay has a cation exchange capacity of 50 to 200 milliequivalents per 100 grams. Nanocomposite material according to claim 1 or 2, wherein the polyolefin matrix is selected from the group consisting of polyethylene and polypropylene. Nanocomposite material according to claim 3, wherein the polyolefin matrix is polyethylene. Nanocomposite material according to any of the preceding claims, wherein the surfactant head group is an ammonium group. Nanocomposite material according to claim 5, wherein the surfactant satisfies the formula (I): R2R2R3R4N + X '(I), wherein - R2 and R2 independently represent a hydrogen atom or a methyl group, 25. R3 is an alkyl group of 1 to 20 carbon atoms, - R4 is an alkyl group of 6 to 20 carbon atoms or a phenylalkyl group comprising an alkyl group of 8 to 18 carbon atoms, - X 'is a counterion selected from the group of halides, sulfates and phosphates. is. Nanocomposite material according to any one of the preceding claims, wherein the weight ratio of the amount of surfactant to the amount of clay is between 0.01: 1 and 100: 1, preferably between 0.05: 1 and 6: 1. 1007434- Nanocomposite material according to any one of the preceding claims, wherein the weight ratio of the amount of clay to the amount of polyolefin matrix is between 1: 200 and 2: 1, preferably between 1:50 and 1.2: 1.5. 9. A method of preparing a nanocomposite material according to claims 1-8, wherein a clay with a layered structure and a cation exchange capacity of 30 to 250 milliequivalents per 100 grams, a polyolefin matrix and a surfactant, which surfactant is a head group an ammonium, pyridinium, sulfonium or phosphonium group, to which two non-polar tails are attached, are mixed together. 10. Modified clay suitable for preparing a nanocomposite material according to claims 1-8, based on a clay with a layered structure and a cation exchange capacity of 30 to 250 milliequivalents per 100 grams, which clay has been modified with a surfactant, which surfactant a head group formed by an ammonium, pyridinium, sulfonium or phosphonium group to which two non-polar tails are attached. 11. A method of preparing a nanocomposite material according to claims 1-8, wherein a modified clay according to claim 10 is mixed with a polyolefin matrix. Molded article made from a nanocomposite material according to claims 1-8, or prepared according to claim 9 or 11. 13. Use of a surfactant, which surfactant comprises a head group formed by an ammonium, pyridinium, sulfonium or phosphonium group, to which two non-polar tails are attached, for modifying clay with a layered structure and a cation exchange capacity of 30 to 250 1007434 * milliequivalents per 100 grams in order to make the clay suitable for inclusion in a polyolefin matrix. 1007434 ^ COOPERATION TREATY (PCT) REPORT ON NEWNESS RESEARCH OF INTERNATIONAL TYPE ION IDENTIFICATION OF THE NATIONAL APPLICATION Characteristic of the applicant or of the community j Nw 1276 | Neouvanden application nr | indieongs date ι 1007434 | November 3, 1997 _i _! Priority oaajm invoked Applicant (Name) j TNO | | Galin of net reconciliation performs an onoerzoex of mterr.aaonaai type Ooor de insanae for (ntemaaonaat Onderzoeno (ISA) to net | reconcile for an investigation of mtemaoonaal type segexeno nr. I SN 30428 NL I. CLASSIFICATION OF THE SUBJECT (with Bepassmg of different dassiAcaoes. specify all dassiftcaoesym Poland) According to the Insmaoortaie da & sificaae (IPC) Int.Cl.6: C 08 K 9/04, C 01 B 33/44 il II. RESEARCHED FIELDS OF TECHNIQUE --------- ---— I __Onaerzccine minimum documentation____ 1 Classifi cation SYSTEM 1 Classrticansvrrcolen _'__ J: i Int.Cl.6: IC 08 K, C 01 B! R I; ti I i 1 I ', I __! __ 1 Researcher cereal information can ae minimum accumenaoe enter as far as the dccumeo®nm included the subsection, i I! ii 'I i ___I j .. NO RESEARCH MCGEL1JK FOR CERTAIN CONCLUSIONS (oomerxmgen co supplementirtgsBfaG'.; I _: | V. '_; GE3REK TO UNITY OF INVENTION (ccmerxincen co a v. Jlincsoiacl V = orrr PDT.ISa :: · a.GE -ï S ^ \ \