Patent Application
20170210860
The present disclosure relates to a process for producing high-resiliency rigid composite material, to a high-resiliency rigid composite material, and to its uses.
Compounding, which is known in the petrochemical and plastics production sectors, is a process that provides for the production of composite materials and consists in mixing together thermoplastic polymers of various polyolefinic nature in a molten state with the use of high friction values (high mechanical shear).
In the background art, one of the limitations of polymerization processes is that they provide polyphasic thermoplastic polymeric materials, which can have a broad and balanced performance set, capable of meeting functional requirements that are required of particular articles.
These processes cannot ensure at the same time rigidity and tenacity of petrochemical-process polymers, since the use of suitable formulation solutions conflicts with:
This is the case of processes for polymerization of polypropylene (PP) in the liquid phase or in the gaseous phase with catalytic systems with a high yield of isotactic polymer, incapable of producing PP materials characterized at the same time by high rigidity and high resiliency at temperatures below −30° C., in which the raw materials used can only be propylene monomer and ethylene comonomer.
The method according to the present disclosure aims at obtaining thermoplastic materials that are composites of polypropylene and have at the same time good properties in terms of rigidity and resiliency, by mixing in a molten state polymers having different characteristics, modifiers, additives and fillers.
The innovation involves using the technology of compounding, which is known for mixing in a molten state polymers with additives and fillers, but which is used in an original way in terms of
With the present disclosure, a process for the production of high-resiliency rigid composite material has been found surprisingly which provides for the non-obvious combination of
This aim and other objects are achieved by the subject matter of the present disclosure.
The present disclosure relates to a process for the production of high-resiliency rigid material, characterized in that it comprises the step of mixing and dispersing in a molten state in a mixer the following compounds:
The present disclosure relates also to a high-resiliency rigid composite material, characterized in that it comprises:
The present disclosure also relates to the use of the composite material according to the present disclosure to produce sheets for thermoforming by extrusion, injection molding of technical cases, molding of containers for electrical/electronic instruments, injection molding of mechanical instruments, injection molding for containers for protecting electronic systems and for appliances, injection molding for components for workplace safety, injection molding for components for the automotive sector.
According to the present disclosure, the term compounding refers to a process that provides for the production of composite materials and includes mixing together thermoplastic polymers of various polyolefinic nature in a molten state with the use of high friction values (high mechanical shear).
According to the present disclosure, the term “compounds” refers to composite materials as obtained from the compounding process.
According to the present disclosure, the values expressed as percentage by weight refer to the percentage by weight of the total weight.
According to the present disclosure, the term “high shear” refers to the high transfer of mechanical work by friction, caused:
According to the present disclosure, the dimensional values expressed and relating to the fillers described here refer to the particle size referred to unit fillers, i.e., to the average size of the diameter measured for said fillers.
The fillers are differentiated according to their average particle size by screening. The dimensions of the fillers are measured by means of various techniques, capable of providing the Gaussian distribution of the dimensions of the elementary particles.
One value that is useful for differentiation of the fillers with respect to their unit size is the value D50, which represents the size of the mesh of a screen through which 50% by weight of the filler subjected to measurement by screening pass. For example, the value D50=2 indicates that at least 50% of said filler passes through a screen with a diameter (or maximum size) of 2 micrometers.
The methods for measuring particle size, in relation to the nature of the powder (electrostaticity, wettability, morphology, etc.) are, among others:
For inorganic fillers of the type indicated in the present document, screening is often used with reference to the ASTM D 422 standard.
According to the process of the present disclosure, the following materials are mixed in a molten state and are dispersed and distributed uniformly in polypropylene matrices:
The result of the molten mixing process, known as compounding, is characterized by the obtainment of composite materials or compounds constituted by a thermoplastic polymeric matrix in which other polymers are dispersed and distributed which have a modifying function, additives, fillers and/or reinforcements.
If necessary, said composite materials or compounds are rendered compatible with the polymeric matrix by adding bonding agents.
The impact modifier polymers, which can have an elastomeric behavior, are also thermoplastic and therefore fall within this category.
To ensure that the corresponding products have the best result in terms of uniformity and constancy of performance, compatibility promoters of the ionomeric or acrylic or maleic type are used which are capable of ensuring that the composites have:
The effectiveness of said compounding process in terms of distribution and dispersion of the modifying ingredients is evaluated by monitoring:
The present disclosure relates to a process for the production of high-resiliency rigid composite material, characterized in that it comprises the step of mixing and dispersing in a molten state in a mixer the following compounds:
The process according to the present disclosure provides for:
Preferably, the step of mixing and dispersing in a molten state, or the dosage of the raw materials that will constitute the compound, occurs gravimetrically or volumetrically. Even more preferably, said step of mixing and dispersing in a molten state occurs gravimetrically.
The gravimetric approach is preferred due to the possibly large difference between the specific gravities of the different ingredients which can constitute the mix.
Gravimetric dosage of the components is preferred in order to ensure that the hopper for the first feeding of the polymeric components operates with imminent filling, preferably without accumulation and with a low head of solid material.
The dosage of the fillers, preferably gravimetrically and with forced feeding, can occur on a molten polymeric mix.
Preferably, said mixer is of the high shear type.
Preferably, in the process according to the present disclosure the step of mixing in a molten state (compounding) also provides for a system for monitoring the absorption of driving power of the motor of the co-rotating twin screw extruder, capable of detecting continuously the mixing work.
Said mixing work is insured:
Preferably, said work imparted to the molten polymeric mass is expressed in kWh/kg.
For example, the process for the production of high-resiliency rigid material according to the present disclosure can comprise the step of mixing and dispersing in a molten state in a mixer the following compounds and in the following quantities expressed as percentage by weight:
With said composition, the best performance set for dispersion and distribution occurs with values of kWh/kg comprised between 0.1 and 0.2.
The present disclosure relates also to a high-resiliency rigid composite material, characterized in that it comprises:
According to the process and the material of the present disclosure, said polymers of isotactic propylene are selected from the group constituted by: homopolymers of propylene and copolymers of propylene.
Preferably, said homopolymers of propylene and copolymers of propylene can have the form of granules, powder or flakes.
Preferably, said homopolymers of propylene have a fluidity comprised between 0.5 and 30 g/10′ or ml/10′.
Preferably, said homopolymers of propylene are present in a quantity comprised in the range of 45-85% by weight.
Preferably, said propylene copolymers have a fluidity comprised between 5 and 30 g/10′ or ml/10′.
Preferably, said propylene copolymers are present in a quantity comprised in the range of 45-90% by weight.
According to the process and the material of the present disclosure, said modifying polymers are selected from the group constituted by: polymers of poly alpha olefins (POE), ethylene propylene rubbers (EPR), ethylene propylene dimer rubbers (EPDM).
Preferably, said polymers of poly alpha olefins (POE), ethylene propylene rubbers (EPR), ethylene propylene dimer rubbers (EPDM) are present in the form of flakes or granules.
Preferably, said polymers of poly alpha olefins (POE) and ethylene propylene dimer rubbers (EPDM) can have a crystalline phase or lack such a phase.
Preferably, said poly alpha olefin polymers (POE) are present in a concentration comprised in the interval of 10-30% by weight.
Preferably, said ethylene propylene rubbers (EPR) are present in a concentration comprised in the range of 5-20% by weight.
Preferably, said ethylene propylene dimer rubbers (EPDM) are present in a concentration comprised in the range of 5-20% by weight.
According to the process and the material of the present disclosure, said compatibility promoters are selected from the group constituted by: olefin polymers functionalized with maleic anhydride, olefin polymers functionalized with silanes, ethylene-acrylic acid (EAA) copolymers, polycaprolactones.
Preferably, said olefin polymers functionalized with maleic anhydride are equivalent to a maleic anhydride present in the range of 0.5-0.8% by weight.
Preferably, said olefin polymers functionalized with maleic anhydride are present in a range comprised between 2 and 5% by weight.
Preferably, said olefin polymers functionalized with silanes are present in a concentration comprised in the range of 0.5-5% by weight.
Preferably, said ethylene-acrylic acid (EAA) copolymers are present in a concentration comprised in the range of 6-12% by weight.
Preferably, said polycaprolactones are in powder or granule form.
Preferably, said polycaprolactones are present in a concentration comprised in the range of 0.5-2% by weight.
The use of compatibility promoters has the purpose of
With an equal composition of the polypropylene matrix, impact resistant polymer, stabilizing additives and fillers and/or reinforcements, the use of a compatibility promoter ensures a better performance balance of the compound.
Said compatibility promoters between the polymeric matrix and the additives also have the function of improving affinity among the fillers used also to increase rigidity.
Said polymers modify the impact resistance properties and facilitate bonds with the polymeric matrix.
In particular, the polymers selected from the group constituted by: acrylic polymers, ionomers, polycaprolactones, polymers with silane and maleic functionality have the function of improving affinity between the fillers and the polymeric matrix, limiting coalescence among the inorganic products used to increase rigidity.
According to the process and the material of the present disclosure, said additives are selected from the group constituted by: phenols, phosphites, ethers, thioethers, benzophenones, benzotriazole derivatives, sterically hindered amines, halogenated additives, melamines, melamine salts, salts of phosphorus derivatives, glyceryl monostearate, stearic salts of calcium, stearic salts of zinc, organic compounds, inorganic salts, inorganic oxides, carbon blacks.
Preferably, said additives are present in a concentration comprised in the range of 0.1-0.5% by weight.
Said phenols, phosphites, ethers and thioethers perform the function of thermal stabilizers.
Said benzophenones, benzotriazole derivatives, sterically hindered amines perform the function of UV stabilizing agents.
Said halogenated additives, melamines, melamine salts, phosphorus derivatives perform the function of flame-retardant additives.
Said glyceryl monostearate, stearic salts of calcium and of zinc perform the function of antiacid and process aids.
Said organic compounds, inorganic salts and inorganic oxides, carbon blacks perform the function of dyes and pigments.
Each composite system (compound), constituted by a polypropylene matrix, impact resistant modifier polymer and compatibility promoter, is completed by the presence of additives, the functions of which are:
Each compound contains stabilizing additives in quantities and qualities that are compatible with the compounding process and with the operating conditions provided for the products obtained from these compounds.
Said additives perform the functions of
Said fillers are selected from the group constituted by: inorganic fillers having an isotropic structure and fillers having an anisotropic structure; wherein said fillers have dimensions of the unit components comprised in the range of 10−3 mm-10−6 mm.
Preferably, said inorganic fillers with isotropic structure are selected from the group constituted by: micronized talc with high purity in silicates of calcium and magnesium, calcium carbonate.
Preferably, said micronized talc with high purity in silicates of calcium and magnesium, has a shape extension of more than 15, with values D50 comprised in the range of 0.2-2 micrometers, in concentrations comprised in the range of 0.5-12% by weight.
Preferably, said calcium carbonate is in the form of a nanofiller and has dimensions comprised in the range of 0.5-0.005 micrometers in a concentration comprised in the range of 0.1-7.5% by weight.
Preferably, said fillers with anisotropic structure are selected from the group constituted by carbon nanotubes and glass fiber.
Preferably, said carbon nanotubes have a shape extension of more than 500; said nanotubes are present in a concentration comprised in the range between 0.5 and 7.5% by weight.
Preferably, said glass fibers are cut with a length comprised in the range of 0.2-4.5 mm, with elementary burr with a diameter comprised in the range of 5-15 micrometers.
Said fillers have the function of supporting the loss in rigidity caused by the presence of impact modifier polymers without compromising the performance balance.
In particular, the use of fillers having small and very small dimensions as defined above, i.e., characterized by values of the unit components comprised between a few micrometers (10−3 mm) and a few angstroms (10−6 mm), advantageously and surprisingly provides the characteristics of rigidity and high resiliency as described in the present disclosure.
In order to compensate for the loss in rigidity induced in the matrix by the use of resilient polymeric modifiers, inorganic fillers are used. These fillers provide different effects as a consequence:
According to the process and the material of the present disclosure, in a first preferred formulation, cited by way of non-limiting illustration of the application of the disclosure:
It is useful to note that this formulation is of unquestionable interest due to the high resiliency that is provided to the material without compromising its rigidity.
According to the process and the material of the present disclosure, in a second preferred formulation, also cited by way of non-limiting example of the application of the disclosure, which therefore does not exhaust the formulations comprised within the protective scope claimed herein:
It is noted that this specific formulation makes it possible to obtain materials that have high resiliency and high rigidity in addition to excellent antistatic properties.
The present disclosure relates also to the use of the composite material of the present disclosure to extrude sheets for thermoforming by extrusion, preferably for an impact-resistant and radio frequency isolation version, injection molding of technical cases, preferably for an impact-resistant and radiofrequency isolation version, molding of containers for electrical/electronic instruments, injection molding of mechanical components, injection molding of protective containers for electronic systems and for equipment, injection molding of components for workplace safety, preferably for helmets, projectile barriers, injection molding of components for the automotive sector.
With reference to the production plants, plants are used which are capable of providing high friction in order to embed the organic and/or inorganic added material uniformly in the matrices of polypropylene.
The plants are extruders of the single-screw type or axial twin-screw type with high rotation rate, provided with forced feeding of molten polymeric material, adiabatic continuous mixers of the two-stage type with underlying extruder/laminator and single-screw extruders rotating with an eccentric element at high-speed (co-kneader).
The geometry of the screws has a variable profile and can be constituted by conveyance and mastication elements, the latter being obtainable with multi-cusp elements (double and triple start), capable of facilitating, together with the advancement of the polymeric flow with imminent softening, a partial regression of said flow.
The feeding of the ingredients into the mixing extruders in a molten state occurs continuously by means of gravimetric or volumetric dosage systems; the feeding of part of the ingredients can occur with molten polymeric material by means of forcing screws for fillers and/or reinforcements.
The mass of molten polymer that contains the modifying ingredients uniformly dispersed and distributed therein by the screws having high masticating capacity profiles is forced through a manifold into an extrusion head and into a die.
The molten mass formed by the die can be:
The process thus described turns out to be inventive and original because:
With reference to the technological method, in order to obtain the compounds of the type according to the present disclosure, the components that constitute the composite material (compound), the physical, thermal and mechanical characteristics of which depend on their mutual concentration, are dosed gravimetrically and continuously in molten state mixers, constituted by:
In a preferred embodiment, the production of the compounds, the performance of which is indicated hereinafter, was performed in a laboratory compounding plant using the following parameters:
Industrial compounding lines repeat in general terms the indicated processing parameters and are the scale-up of the technological set used in the laboratory to produce the industrial compounds according to the claims that follow.
The following are examples aimed at better explaining the subject matter of the present disclosure.
Table 1 lists some characteristics of polypropylene without and with ethylene comonomer in various concentrations: the polymers being considered have comparable fluidity values and their predominant technological destination relates to their transformation by injection molding.
All the polypropylene types exemplified in Table 1 have impact resistance characteristics that are insufficient to be polymeric matrices that are interesting for being modified with fillers and/or reinforcements, the purpose of which is to reach higher rigidity values.
The aim of the present disclosure is to modify the polypropylene matrix in order to obtain an optimum performance balance so as to manufacture products that require high rigidity and impact resistance values at the same time.
Ethylene-propylene copolymers with appropriate rheology in the molten state, among these in particular those with a partially crystalline morphology such as POE (Poly Olefin Elastomers), if used in concentrations compatible with the preservation of suitable rigidity values, provide the thermoplastic matrices of polypropylene nature with important benefits in terms of increasing their impact resistance.
The innovative elements reside:
The following Table 2 exemplifies the variations undergone by matrices of polypropylene (PP) with POE modifiers.
As described above, in order to compensate for the loss in rigidity caused to the PP matrix by the use of resilient polymeric modifiers, inorganic fillers are used. These fillers impart different effects as a consequence:
The innovative elements of the present disclosure reside:
The following Table 3 exemplifies the beneficial effects achieved on the performance of a PP matrix with simultaneous use:
The performance set of composite materials containing a polypropylene matrix, a polymeric modifier and variable percentages of talc filler in micronized form, shown in the following Table 4, provides evidence of the containment of the resiliency loss together with the increase in rigidity.
Types of talc with different particle size, dispersed and distributed during mixing in the molten state in a matrix of PP modified with elastomeric polymer, contribute differently to the performance blend of rigidity and resiliency, usually associating lower rigidity with a higher resiliency value.
According to the results of the present disclosure it is possible to associate a better balance of rigidity and resiliency with equal density by using the same mixing technology, the same combination of PP matrix and modifier, using a more micronized talc filler.
Innovative elements with respect to current knowledge are constituted by the results, obtained by the use in the matrix of PP modified with POE with the prospect of improving resiliency without a significant loss in rigidity, of different concentrations of nanofiller of calcium carbonate, as shown in Table 6.
The PP matrices, improved in their resiliency by adding elastomeric polymers (POE), are interesting polyphasic systems capable of containing nanoreinforcements (carbon nanotubes), with the prospect of increasing rigidity and obtaining an antistatic behavior, as is evident from the examination of the performance listed in Table 7.
For high contents of carbon nanotubes, electrically conducting thermoplastic composite materials are obtained which have a shielding effect against radio frequencies and electromagnetic waves.
material, a high-resiliency rigid composite material, and uses thereof
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IT2014/000196 | 7/25/2014 | WO | 00 |
