WO2016064405A1

WO2016064405A1 - Composition of an insulating pvc substrate with nanoparticle treated filler

Info

Publication number: WO2016064405A1
Application number: PCT/US2014/061983
Authority: WO
Inventors: Jimmie R. Baran, Jr.; Vanessa C. ARANTES; Rodrigo M. TAFURI; Manuela Lima Queiroz de Andrade KANEKO; Aileen N. FOWLER ZANIN
Original assignee: 3M Innovative Properties Company
Priority date: 2014-10-23
Filing date: 2014-10-23
Publication date: 2016-04-28
Also published as: TW201615721A

Abstract

The present invention refers to a composition for an insulating substrate comprising a polyvinyl chloride (PVC) resin and a dispersion of nanoparticle treated inorganic filler. In one aspect, an insulating adhesive tape can be made from the composition.

Description

COMPOSITION OF AN INSULATING PVC SUBSTRATE WITH

NANOP ARTICLE TREATED FILLER

TECHNICAL FIELD

The present invention refers to a composition of an insulating substrate, specifically insulating adhesive tape made from (poly) vinyl chloride (PVC), with the addition of fillers previously treated with nanoparticles.

BACKGROUND

The polymer industry has become even larger in recent years. This is due to the immense range of possible applications of the polymeric materials; which is a result of the great fiexibility that their characteristics possess. Specifically, polyvinyl chloride, better known as PVC, has been broadly used to manufacture different types of materials, including insulating films and tapes. However, it is necessary to incorporate additives into the PVC so that it may confer on to the end products, the various characteristics desired.

Tapes currently used in the electrical industry, for example, which provide electrical insulation, are normally made from PVC. Thus, to improve their electrical insulation, flame retarding and thermal stability characteristics, additives must be added to the PVC during the production of the film. Such additives include ceramic materials and mineral fillers such as Ca/Zn stearate, pigments, flame-retardants and UV stabilizers, among other fillers. Flame-retardants are used to keep a fire from starting, inhibiting ignition and delaying or preferably eliminating flame propagation, while other mineral fillers, such as functionalized CaC0₃, are added to improve the mechanical properties of the PVC.

A key factor for improving the flame retarding properties of PVC polymers has to do not only with the types of filler added to the PVC matrix, but above all the high quality of the dispersion of the said fillers added to the PVC.

We found that prior treatment of the fillers to be added to the PVC with nanoparticles improved its flammability properties without changing the other properties, such as its mechanical and electrical characteristics. Nanoparticles promote better dispersion of the fillers within the polymeric matrix, including dispersion of the flame retardant, improving the properties of the end product, and making it possible to reduce the amount of functional materials used.

One of the flame retardants most widely used in PVC formulations is antimony trioxide. However, in recent years the supply of this material has drastically reduced, leading to a substantial increase in cost. Currently, a number of other materials have been tested to replace antimony trioxide. Some phosphorus-based plasticizers and inorganic fillers such as alumina have been tested, however these materials must be used in an amount up to ten times larger than that of the amount of antimony trioxide normally used to confer the same flame retarding effect. Furthermore, the use of such materials, because of the huge amounts required, impart other negative characteristics to the end product. Thus, there is an enormous interest in improving the technology in a pursuit to find suitable materials that can be used to reduce the f ammability of PVC products without the need to use large amounts of antimony trioxide.

In addition, an alternative related to improving the dispersion quality of all additives in PVC compounds is being sought, so as to optimize their performance and minimize material costs as described above, while at the same time achieving the same results as those achieved using larger amounts of antimony trioxide. Alternatively, there is a desire to increase the concentration of low-cost fillers in order to reduce the overall cost of the end product. Thus, we found that by treating at least one of the fillers with nanoparticles, it is possible to achieve the same result as that achieved with larger amounts of antimony trioxide.

As references for the state of the art of this technology, we found the following documents that include technologies related to the present invention.

The document US 8062670 refers to powder compositions with improved flow properties. These compositions are comprised of a powdered solid material which possesses a surface that has been modified with nanoparticles. Methods to improve the flow of powder compositions, as well as devices and articles produced from using such compositions are also described.

The document EP 705881 refers to a reinforcing agent for thermoplastic polymers comprising at least one impact modifying additive and a synergistic combination of a micronized silica and at least a material containing calcium selected from among calcium carbonate, calcium stearate and calcium hydroaluminate Ca6Al(OH)15. The impact modifying additive of the present document has the characteristic of avoiding agglomerates, thus improving the fluidity of the composition, which includes at least two inert fillers. The synergistic composition thus includes a micronized silica and at least one calcium compound from among those described above. According to the invention, calcium carbonate is coated, preferably with a calcium salt of a higher fatty acid containing at least 12 carbon atoms, ideally stearic acid. This coating is performed in a conventional manner, preferably at a temperature of between 60 and 200 degrees Celsius. Said coating coats practically all of the particles individually.

Document WO 201147778 refers to treated mineral fillers, to the process for their preparation and to their preferred use in plastic applications, preferably in applications for polypropylene (PP) or polyethylene (PE) based coating films.

Document EP 1487912 refers to cross-linked and cross-linkable nano filler compositions, the processes for its preparation and articles with the same respective contribution. In particular, this document refers to cross-linked and cross-linkable nanofillers containing ethylene polymers, such as polyethylene. These nanofiller combinations have advantageous properties such as increased barrier properties, resistance and higher heat distortion temperatures, making them useful in diverse applications, including medical, automotive, electrical, construction and food applications.

PCT/AU92/00375 refers to a sheet or panel of sound insulating material comprising: (a) a polymeric component free of bitumen or asphalt, such as natural or synthetic rubber, PVC, chlorinated polyethylene or ethylene vinyl acetate copolymer; (b) a filler such as calcium carbonate, barites, talc, mica, magnesium carbonate or silica; and (c) a compatibilizing agent such as ricinoleic acid; an agglutinating agent such as pine rosin. Formulations may include a flame retardant, a polar additive, a polymer anti-oxidant, a PVC heat stabilizer and a lubricant. Methods for forming such sheets or pads and for applying such sheets or pads to a metal panel are also provided.

Document EP 1698657 refers to a PVC composition that has high thermal stability, surface quality and notched-impact- strength, comprising: polyvinyl chloride components with a K-value of 55-80 in accordance with international organization for standardization 1628-2, calcium carbonate with a nanometer range particle size and a coating of stearic acid, with a high impact modifier, a blend of stabilizers and titanium dioxide. The PVC components and calcium carbonate are blended for 30 to 60 seconds in a hot/cold mixer before the remaining components are added. SUMMARY

The object of the present invention is to provide a composition for a PVC based insulating substrate with a nanoparticle treated filler. Specifically, nanoparticle treated micronized calcium carbonate (CaC0₃) mineral filler and flame retardant to be used in PVC films, in particular reducing the fiammability and enhancing the thermal resistance characteristics of the PVC as a result of the improved disbursement of the fillers.

BRIEF DESCRIPTION OF DRAWINGS

This invention shall now be described in respect to the attached drawings, where:

Figure 1 is a 400 times magnification scanning electron microscope picture of a sample from comparative example 1, as described in Table 2.

Figure 2 is a 400 times magnification scanning electron microscope picture of a sample from example 4, as described in Table 2.

Figure 3 is a 600 times magnification scanning electron microscope picture of a sample from example 1, as described in Table 2.

Figure 4 is a 600 times magnification scanning electron microscope picture of a sample for comparative example 2, as described in Table 2.

Figure 5 illustrates the result of the mass loss test for the samples of the present invention, example 4 and comparative example 1, as described in Table 2.

Figure 6 illustrates the result of the volatilization test for the samples of the present invention, example 4 and comparative example 1, as described in Table 2.

DETAILED DESCRIPTION OF THE INVENTION

Below is a detailed description of the object of the present invention. It is intended merely as an example and not intended to limit the scope of the present invention in any way, as both the material and production method itself as revealed herein may comprise different details and structural elements, procedures and dimensions without going beyond the scope of protection intended.

As mentioned above, improving the flame retarding properties of PVC polymers depends not only in the type of filler added to the PVC, but also on the quality of the dispersion of the fillers added to the PVC.

Given the observation of the known problem of agglomeration, and thus poor dispersion of the inorganic fillers added to (poly) vinyl chloride (PVC), the investigators proceeded to test the treatment of the said inorganic fillers with small amounts of nanoparticles.

In this application:

The term "nanoparticle" as used herein (unless an individual context specifically implies otherwise) will generally refer to particles that, while potentially varied in specific geometric shape, have an effective, or median, diameter of less than 100 nanometers. Although the particles may be agglomerated, they are not aggregated.

"Non-aggregated nanoparticles" refers to individual (discrete) particles or agglomerated particles not bonded together by at least one of covalent bonding, hydrogen bonding, or electrostatic attraction. Fumed silica particles are known in the art to be aggregate particles, including aggregates of nanoparticles. Therefore, fumed silica having a (aggregate) particle size of at least 100 nm, even if made up of silica nanoparticles, would not be non-aggregated nanoparticles.

The investigators found that prior treatment of the fillers to be added to PVC polymers with nanoparticles improved the flammability properties of the PVC polymers without changing other properties, such as their mechanical and electrical characteristics. Treatment with nanoparticles promotes better dispersion of the fillers within the polymeric matrix, including dispersion of the flame retardant, thus improving the properties of the end product, and making it possible to reduce the amount of functional materials used. Modifying the inorganic fillers with nanoparticles not only improves the flame retarding characteristics of the PVC products, but it also reduces the use of high cost fillers such as antimony trioxide, resulting in a lower final cost of the PVC product.

Therefore, one objective of the present invention is the use of nanoparticle treated filler to improve the flame retarding characteristics of polymeric materials, more specifically, the use of silica nanoparticles in calcium carbonate (CaC0₃) and antimony trioxide (ATO) mineral fillers, promoting better filler dispersion and thus improving the thermal stability of PVC based products, leading to more efficient flame retardation. More specifically, the present invention refers to using nanosilicas to treat inorganic fillers to be added to adhesive insulating tapes.

Treating fillers to be added to polymeric materials with nanoparticles has the following advantages: It reduces the problem related to the presence of holes in vinyl films, which adversely affects the mechanical properties of such film, thus reducing material losses during the manufacture of the product;

More homogeneous product properties;

Larger amounts of filler may be incorporated;

Increases the volumetric density of the filler, resulting in easier processing;

Maintains the product's flame retarding properties, reducing the amount of flame retardant used by 50%.

Treating inorganic filler, more specifically micronized calcium carbonate filler comprised of at least 80% calcium and 10% magnesium, and a known retardant such as antimony trioxide (ATO) with nanoparticles is a typical example of the efficacy that nanoparticles possess for improving the flame retarding properties of PVC. In some embodiments of the composition, more than one type of inorganic filler material may be used. If more than one type of filler material is used in the composition, one filler type may be surface treated with nanoparitcles and the other(s) may be untreated, or each filler may be surface treated with nanoparticles.

In some embodiments, the nanoparticles have a primary particle size of not greater than 20 nm; in some embodiments, not greater than 15 nm, 10 nm, or even not greater than 5 nm. In other embodiments the nanoparticles preferably have a primary particle size in a range from 1 nm to 100 nm, or even from 4 nm to 20 nm.

The nanoparticles selected for treating the mineral filler and flame retardant used in the PVC compound may be selected from the group comprised of zirconia, zinc oxide, calcium phosphate, gold, silver, iron oxide and silica, among others. The nanoparticles of the present invention preferably comprise nanosilicas. The nanosilicas are most preferably, non-agglomerated surface modified.

The nanoparticles, preferably non-agglomerated surface modified nanosilicas, were treated according to the procedure described in United States Patent no. US 8,062,670, which has been incorporated by reference herein in its entirety.

The amount of nanoparticles used in the present invention ranges from between about 0.07%) and about 0.42% by total product weight, more specifically between about 0.07%) and about 0.21% by weight of product.

The ratio in terms of weight of inorganic filler to nanoparticles ranges from between 100/0.5 and 100/3, most preferably between 100/0.5 and 100/1.5,

PVC based compounds suitable for the present invention have a composition comprising about 45 to about 60% by weight of a PVC resin with a K value of about 65 to about 70, about 1 to about 5% of a Ca/Zn heat stabilizer and about 15 to about 35% of monomeric DINP (di-isononyl phthalate) plasticizer. Examples of commercially available PVC resins are SP1000 and SP1300 manufactured by Braskem (BR); examples of commercially available heat stabilizers include CZ6200 by Chemson, and examples of DINP plasticizers include those commercially available from Elequeiroz (BR) and Exxon. In some embodiments, the composition of the present invention comprises between about 70%) and about 97% by weight PVC based compound, based on the total weight of the composition.

Some aspects of the invention comprise inorganic fillers such as flame retardants and calcium carbonate (CaC0₃). In some embodiments, the composition of the present invention comprises between about 3% and about 30%> by weight inorganic filler, based on the total weight of the composition.

Flame-retardants suitable for the present invention include, but are not limited to antimony trioxide (ATO). Examples of commercially available flame-retardants include those that comprise antimony trioxide made by Oxy Quimica. In some aspects of the present invention, the composition comprises between about 1% and about 10%> by weight of flame retardant.

A purpose of CaC0₃ is to improve heat resistance, as well as to reduce the final cost of PVC film, without affecting its mechanical characteristics. CaC0₃ suitable for the present invention is micronized; that is, it has a particle size of between about 1 and 20 microns, preferably between about 1 and 10 microns, and more preferably between about 1 and 3 microns. Suitable CaC0₃ includes material commercially available from, for instance, Micronita (www.micron-ita.com.br) and Provale (www.provale.ind.br). In some aspects of the present invention, the composition comprises between about 2% and about 20% by weight of CaC0₃.

Compositions of the present invention can be calendared into films and used as a backing for tape. Adhesive may be coated onto the film, which can be converted into rolls to yield a tape. Examples of the adhesive include pressure sensitive adhesives and rubber based adhesives. EXAMPLES

The examples and comparative examples that follow are offered to help understand the present invention and should not be interpreted as limiting its scope. Unless otherwise indicated, all of the parts and percentages are by weight. The following test methods and protocols were used to assess the illustrative and comparative examples that follow.

Table 1. List of Materials Used

Nanosilica particles were modified with isooctyltrimethoxysilane and methyltrimethoxysilane (Aldrich Chemical, US) according to the procedures described in United States Patent no. US 8,062,670. To prepare nanosilica treated ATO and CaC0₃ fillers, 50 g of filler (either ATO or CaC0₃) and 500 mg of surface modified nanosilica were placed in an intensive mixer (SPEEDMIXER DAC 15-FVZ, FlackTek Inc, USA) and processed at 3,000 rpm for 60 seconds; the mixture was processed 3 times. The nanosilica treated filler was then used without being submitted to any further purification process.

Nine samples were prepared: Examples 1, 2, 3 and 4, and Comparative Examples CE1, CE2, CE3, CE4, and CE5. The PVC formulations in Table 2 were prepared using the following steps:

Step 1 : Blending all of the materials in a high-speed mixer at a temperature of

100°C.

Step 2: Melting the product of Step 1 in a twin-screw shearing extruder at a temperature of 180°C. Step 3 : Processing the molten material in a calender to produce a film.

Table 2

The following tests and analyses are provided as an additional illustration of the compositions and effects of the present invention.

SEM (Scanning Electron Microscope) Analysis

SEM analyses were performed in order to verify the dispersion of the filler in the PVC matrix when using the nanotreated fillers. A 15kV, 300, 400 and 600x magnification was conducted using an Inspect S 50 model, FEI (US) brand microscope, with a composition detector.

Figures 1 and 2 compare the formulation of comparative example CE1 (Figure 1) and the formulation of example 4 (Figure 2). The fillers can be seen in the SEM micrographs as the grey particles (CaC0₃) and white particles (ATO). Figures 1 and 2 show that not only is the CaC0₃ better dispersed when treated with nanosilica, but, surprisingly, the untreated ATO is better dispersed as well. The better dispersion is evidenced by the smaller size of the particles that are more homogeneously distributed throughout the PVC matrix.

Furthermore, the investigators analyzed the effects of nanotreatment on filler dispersion using half the amount of ATO normally used in PVC films (comparative example CE2), before and after treatment with the nanoparticle: Figures 3 and 4 show the results of said to analysis for the formulations of example 1 (with treated ATO) and comparative example CE2 (with untreated ATO).

One may conclude that the nanotreated ATO (example 1 formulation) is better dispersed in the PVC matrix, as can be seen in figure 3. The same effect was not observed in the images obtained for the film with untreated ATO (formulation of CE2), as shown in figure 4.

In addition, comparative tests were conducted employing fumed silica as specified in Table 2. CE4 and CE5 were compared with example 4. SEM images showed that the example 4 had better dispersion of CaC03 compared to CE4 and was slightly better when compared to CE5. It is therefore concluded that the use of surface modified nanosilica yields reduced agglomeration of the particles within the matrix polymer, in comparison to fumed silica.

Resistance to Flame Propagation

The resistance to flame propagation test was performed on the samples listed in Table 2. Each sample was 300 mm long and 19 mm wide. A marking was made in the lower part of each sample (50 mm) and flame indicator paper was applied. The cone of a Bunsen burner flame was applied to the indicator paper and the length of the burnt tape was observed.

Table 3 shows the results of the flame resistance test:

Table 3

Specification:

Maximum 50 mm burn length

Sample Flammability (mm)

Comparative Example 1 26

Comparative Example 2 Burnt

Comparative Example 3 Burnt

Comparative Example 4 30

Comparative Example 5 22 Example 1 18

Example 2 18

Example 3 18

Example 4 16

Comparing the formulations of comparative examples 1, 2 and 3 with that of example 1 it is found that the addition of treated ATO to the formulation may at least halve the amount of ATO added while maintaining the same flame propagation behavior.

When comparing the formulation of CE1 with that of examples 2, 3 and 4, it was found that the treatment with the CaC0₃ filler has a direct influence on the material's flammability properties. Thus, it may be concluded that improved dispersion of the filler results in an improvement in the flame retardant properties of the formulation.. In addition, one can use less flame retardant to achieve the desired level of flammability.

A comparison of Comparative Examples CE4 and CE5 with Example 4 shows that the use of surface modified nanosilica does not permit agglomeration of the particles as can occur using fumed silica, providing a better dispersion and consequently a better flammability property.

Thermal Resistance (Mass Loss)

This test measures loss of mass after the sample has been exposed to a temperature of 150°C for 480 hours. Results are reported as a % of mass lost, and are shown in Figure 5. A reduction in mass loss indicates an improvement in a tape's thermal resistance. The samples were weighed before being placed in the oven and the loss of mass was measured after 480 hours.

As can be seen in Figure 5, there was a large reduction in mass loss when using the treated filler, resulting in improved thermal resistance of the PVC film. The results of mass loss of formulations using fumed silica were the same as found for formulations using surface modified nanosilica.

HC1 Volatization Test

The HC1 volatilization test is a simple and practical test to demonstrate the effectiveness of adding CaC0₃ for preventing the degradation of the PVC film due to increases in temperature. In this test, the sample is placed in a glass tube and exposed to a temperature of 200°C. A color-indicator pH strip is placed at the mouth of the tube; the time it takes for the color of the strip to change is related to the start of HCl evaporation from the PVC material. The result is reported in minutes of exposure. Longer times are associated with improved thermal stability of the formulation.

Figure 6 shows the results of the volatilization test. Figure 6 shows there was an increase in the time it took for the onset of HCl volatilization for the formulation using treated CaC0₃ (example 4), which indicates enhanced thermal stability.

Mechanical and Electrical Properties

The procedures in ASTM D 1000/10 were followed for the mechanical and electrical testing performed on the samples in Table 2. The results are shown in Table 4.

Table 4 - Electrical and mechanical properties

Elastic memory I seconds ) 1.1 | 0.8 | 0.9 | 0.9 | 0.8 | 0.9 | 0.7

The results presented in Table 4 show there was no change in the electrical and mechanical properties of the film using nanoparticle treated and untreated fillers.

One may conclude that embodiments of the present invention solve one or more of the aforementioned problems of the current state of the art.

It is important to note that the description above is merely an example of some of the preferred embodiments of the present invention. Therefore, it will be clear to those versed in the art that numerous modifications, variations or combinations of elements performing the same function in substantially the same way to achieve the same outcome are within the scope of protection as defined by the attached claims.

Claims

WHAT IS CLAIMED IS:

1. A composition for an insulating PVC substrate, comprising a polyvinyl chloride resin and a dispersion of nanoparticle treated inorganic filler.

2. A composition according to Claim 1 above, wherein the nanoparticle is selected from among the group comprised of zirconia, zinc oxide, calcium phosphate, gold, silver, iron oxide and silica, among others.

3. A composition according to Claim 2, wherein the nanoparticle is nanosilica.

4. A composition according to Claim 3, wherein the nanoparticle is a surface-modified non-agglomerated nanosilica.

5. A composition according to Claim 1 , wherein the nanoparticles are present in an amount ranging from between about 0.07% and about 0.42% of the final polymeric product.

6. A composition according to Claim 5, wherein the nanoparticles are present in an amount ranging from between about 0.07% and about 0.21% of the final polymeric product.

7. A composition according to Claim 1 , wherein the ratio of inorganic filler to nanoparticle by weight varies between about 100/0.5 and about 100/3.

8. A composition according to Claim 7, wherein the ratio of inorganic filler to nanoparticle by weight varies between 100/0.5 and 100/1.5.

9. A composition according to Claim 1, wherein the nanoparticles have a primary particle size in a range from 1 nm to 100 nm.

10. A composition according to Claim 1, wherein at least one filler is treated with a non- agglomerated surface nanosilica.

1 1. A composition according to Claim 1 , wherein the filler may be selected from among inorganic fillers, including calcium carbonate and antimony trioxide.

film comprising the composition of Claim 1

13. A tape comprising the film of Claim 12.