WO2013166568A1

WO2013166568A1 - Polyolefin granulation method, polyolefin resin, polyolefin fibre, use of polyolefin fibre and cement composites

Info

Publication number: WO2013166568A1
Application number: PCT/BR2013/000141
Authority: WO
Inventors: Mauro alfredo SOTO OVIEDO; Cristovão de LEMOS; Fabiana PIRES DE CARVALHO
Original assignee: Braskem S.A.
Priority date: 2012-05-07
Filing date: 2013-05-03
Publication date: 2013-11-14
Also published as: CN104619753B; AR091809A1; BR102012010783A2; CN104619753A

Abstract

The present invention relates to a method for producing polyolefin with enhanced polar character by incorporation of surfactants in order to provide polymer resins used for the production of fibres with improved performance that can be used as reinforcing agents in cement composites. More specifically, the polyolefin obtained by polymerization is modified by incorporation of surfactants during the granulation process. Also described is a polymer resin of improved polarity consisting of a polyethylene homopolymer or a polypropylene homopolymer, copolymer or terpolymer, or a blend of two or more of these components, and at least one non-ionic and/or ionic surfactant having a partially polar structure for preparing reinforcing fibres for use in cement composites for manufacturing structural and non-structural components in the field of civil engineering, such as bridge girders, slabs, pavements, large concrete containers, sealing panels, high-performance tiles, inter alia.

Description

Report of the Invention Patent for "POLYLEPHINE GRANULATION PROCESS, POLYLEPHINE RESIN, POLYLEPHINE FIBER, POLYLEPHINE FIBER USE AND CLENTENT COMPOSITE".

The present invention relates to a process for producing polyolefins such as polyethylene, polypropylene or ethylene propylene copolymer or ethylene propylene butene terpolymer or a blend comprising two or more of these more polar components from the incorporation of additives for obtaining polyolefin resins, whose fibers provide a high performance to act as a reinforcing agent in fiber cement composites. More specifically, the polyolefin obtained via polymerization is modified by incorporating surfactants into the granulation process.

Description of the prior art

The construction market has increased significantly in the last decade, mainly due to the improved quality of life of developing countries. In addition, housing programs, urban mobility and global socio-economic events have contributed to the growth of this sector. The need for materials that meet the growth of this segment has motivated the search for products that are competitive and perform well. One of the main raw materials used in these segments are cement-based products, due to their excellent versatility, and can meet the specific environmental demands to which they will be subjected, projected architectural configuration, durability, technical and sustainability requirements.

However, cement-based products may have cracks which, when subjected to stress, cause their rapid propagation, reducing the mechanical strength of the material. Thus, the introduction of natural or synthetic fibers improves the performance of the concrete, since it can obstruct the propagation of micro cracks, delaying its onset and increasing its strength. Fiber cement composites have greater ductility, bending capacity and resistance to fracture when compared to non-fiber reinforced materials, being used, for example, in the low cost construction industry, especially in the construction of roofs in housing, rural facilities, industrial warehouses and infrastructure works.

In recent decades, asbestos has been widely used in developing countries as a reinforcing agent in cement products due mainly to its low cost, availability and energy saving. Asbestos has good dispersion properties in aqueous suspension without formation of agglomerates, good thermal, chemical, electrical and mechanical properties, the latter being the most important property, as it gives the final product a higher tensile strength.

Asbestos is used for the production of fiber cement sheets in the Hatschek process, in which a diluted suspension of asbestos fibers, cement and additive is mixed in a large tank where rotating cylinders capture this paste by suction, removing water from the mixture until obtaining plates of desired thickness. However, as a result of the potential risks to human health posed by asbestos, new technologies and materials, such as natural and artificial fibers, have been researched in both industry and academia, without neglecting their performance and competitiveness in the face of this problem. to asbestos.

Among the main materials used to replace asbestos are PVA - poly (vinyl alcohol) fiber, PAN - poly (acrylonitrile) fiber, glass fiber, cellulose fiber and PP - polypropylene fiber.

PVA fiber was the first material to be used on a large scale due to its intrinsic properties such as high tensile strength, high modulus of elasticity, high alkaline matrix strength, hydrophilic behavior, good water dispersion and good adhesion with materials. cement-based. These properties mentioned for PVA fibers are also characteristic for PAN fibers. However, both materials require large and often impractical investments in developing countries. Fiberglass, in turn, has high mechanical resistance but low durability in alkaline medium. To ensure better performance of this material in alkaline media, the surface of these fibers should be modified by the addition of components. However, this solution is not commercially competitive.

Vegetable fibers, such as cellulose, in spite of the low cost of the raw material, present unsatisfactory performance due to the low adherence with the cementitious matrix, low resistance to alkaline medium and humidity.

Finally, PP fibers have the lowest cost attractiveness and are used in many applications due to their good properties, such as high ductility, high specific energy, low moisture absorption and low density. However, the hydrophobic character and low roughness are properties that can compromise the adherence and anchorage of PP fibers to the cementitious matrix, respectively.

The final properties of a reinforced fibro-synthetic composite strongly depend on the properties of the individual components, the reinforcement concentration present in the composite and especially the interfacial interaction between the matrix and the reinforcement. Therefore, physical or chemical modification of the fiber surface may be an alternative to obtain a composite with desirable properties. The state of the art proves that technical efforts have been directed towards surface modification of PP fibers with the objective of improving the interfacial matrix-fiber interaction. US 20060234048 describes the use of antistatic agents, surfactants, hydrophobic grease chain polymer compounds having polar functional groups as polyolefin fiber modifiers. The document cites the use of polyalkylene glycols such as polyethylene glycol (PEG) and polypropylene glycol (PPG) as fiber lubricants at a concentration of 0.05 to 5% (w / w). These modifiers are applied to the fiber surface which is used in the production of fiber cement tiles. However, in this technique there is the addition of the modifying agent in the step after fiber stretching (spinning step). In this coating process a good adhesion of the additive to the surface of the polymeric fiber is not achieved. rich as it is lost during the Hatschek process and therefore compromises fiber performance as reinforcement. Furthermore, the increase in adhesion strength presented in this document does not refer directly to the chemical bonding energy between fiber and matrix, but only to the effect of the additive on the cementitious formulation.

The modifying agent described in US 2006234048 is added to the polyolefin fiber at one or more stages of the spinning process, with the function of improving the stretching of the yarn during its transportation in the various stages of production, thus minimizing the electrostatic charges from the spinning process. production. Such modifying agents may be added in pure form, dilute solution, dispersion or emulsion. Contact of the modifying agent with the polymer mixture in the presence of water may still have the drawback of foaming during the process.

US6258159 describes an increase in the hydrophilicity of the PP fiber surface by the addition of additives in the melt during the PP fiber production process, which eventually migrate to the surface as they do not interact with the PP. matrix.

Modification only at the fiber production stage may compromise the dispersion of these additives in the polymeric matrix, impairing the cement-fiber-matrix interface. In addition, the surfactants described in US 6,258,159 are silicone surfactants, polysiloxanes, fatty acid esters, and polytetrahydrofuran which are chemically considered antifoam (avoids foaming). Such compounds with the defoaming function are often used in the reaction medium for producing PP fibers. On the other hand, the nonionic surfactants used in US 6258159 belong to the family of polyether polyols, and have dispersing characteristics, with the final system performance being affected by the surfactant lipophilic and hydrophilic balance (HLB), that is, this HLB balance affects the dispersion of surfactant in the polymeric matrix.

PP fibers can also be modified by surface treatment such as texturing, corona treatment, plasma, flame and chemical position. However, these solutions are of high complexity and high cost, making them industrially unviable.

Conventionally, the addition of the modifier only in the spinning step of a polypropylene fiber, whose process is in aqueous medium, may result in leaching and / or foaming losses, as the surfactant does not have good adhesion to the fiber, causing ease of leaching. .

The present invention describes the addition of nonionic and / or ionic surfactants to the polyolefin resin during the granulation step, ie, step prior to the spinning process. Thus, the increased adhesion between the PP fiber and the cementitious matrix is a consequence of the addition of this modifying agent to the PP resin during granulation and not to the spinning step as described in the prior art.

Additionally, the present invention provides for the addition of a surfactant having a polar and a nonpolar part that contributes to the increase in hydrophilicity of the PP fiber surface, which in turn improves the anchoring of the polymeric fiber to the cementitious composite constituents.

In view of the weaknesses of the techniques that make up the state of the art in the segment of synthetic fiber composites, where in most cases the modification of polypropylene, obtained after polymerization step, with the use of other materials such as maleic anhydride, methacrylate glycidyl and acrylic acid, presents an innovative solution involving the incorporation of nonionic and / or ionic surfactants in polyolefins in the granulation step. These nonionic and / or ionic surfactants may also be termed as surfactants or modifying agents.

In addition, the process described in the present invention not only makes polyolefin more competitive in the market, but also promotes increased surface polarity of polyolefin fiber (higher surface tension) and therefore greater adhesion as a cementitious composite by incorporating surfactants nonionic and / or ionic.

Objectives of the invention

The main object of the present invention is to provide a process for the preparation of a modified polymeric resin with non-surfactant ionic and / or ionic, involving the addition of said surfactant to said post-reactor resin, that is, during the granulation step of the molten polyolefin spheres, with subsequent pelletization of that material.

The present invention also aims to describe a modified polar polymeric resin having a higher polarity and incorporating at least one nonionic and / or ionic surfactant in a polyolefin selected from polypropylene homopolymer or ethylene homopolymer or ethylene copolymer -propylene or ethylene-propylene-butene terpolymer or a blend comprising two or more of these components via the granulation process, promoting an increase in the surface polarity of the polyolefin fiber and, consequently, a higher surface tension of the fiber.

The modified polymeric resin of the present invention is employed in the fabrication of lower surface tension fibers, allowing its better dispersion and adhesion in cementitious composites with excellent mechanical properties.

The present invention also discloses a polyolefin fiber having surface polarity and comprising a polymeric resin modified with ionic and nonionic surfactants obtained via granulation.

Finally, the present invention relates to the use of polyolefin fiber which is used as a reinforcement material in cementitious composites as well as to a cementitious composite comprising said polyolefin fiber.

Brief Description of the Invention

The present invention describes a process involving the addition of surfactants to the post reactor resin, that is, the additive is performed at the granulation stage of the molten polyolefin spheres, with subsequent pelletization of that material, providing a modified polymer resin more specifically, modified polyolefin resin with nonionic and / or ionic surfactants.

The present invention has as advantage the production of polyolefin resin modified by incorporation of nonionic and / or ionic surfactant by the granulation process, which will be used in the manufacture of polyolefins fibers with higher surface polarity (surface tension), allowing having its best dispersion and adhesion in cementitious composites, resulting in a product with excellent mechanical properties.

In addition, the present invention has the advantage of the low incorporation cost to obtain the polyolefin resin whose fibers have greater polar character, which in turn makes this solution more competitive.

Another advantage of the granulation process of the present invention is that the modifying agent (surfactant) is added only in pure form through a specific device coupled to the extruder (liquid metering pump).

During the granulation process, the modifying agent is mixed into the polymeric matrix in the melt state and under shear which contributes to better incorporation of this additive into the polyolefin resin.

In addition, surfactants are often employed to modify the reaction medium to solubilize low solubility species or to promote a new medium that can modify the reaction rate. Addition of surfactants to a polymer in the molten state during the granulation step has not been described or suggested in the state of the art.

Thus, the state of the art refers to modifications of the polyolefin fiber while the present invention provides for modification of the polyolefin resin. Addition of the surfactants to the polyolefin granulation step of the present invention allows for better incorporation of the surfactants into the resin and consequently provides increased adhesion between the polyolefin fiber and the cementitious composite without leaching losses.

Brief Description of Drawings

The present invention will hereinafter be described in more detail based on an exemplary embodiment shown in the drawings. The figures show:

Figure 1 is an atomic force microscopy image of pure polypropylene fiber;

Figure 2 is a picture of surfactant polypropylene fiber 1.

Detailed Description of the Invention The technology developed in the present invention proposes a process involving the addition of surfactants in the post reactor resin, that is, the additive is performed in the granulation stage of the molten polyolefin spheres, with subsequent pelletization of this material. Modified polymer resins, more specifically, modified polyolefin resin of polar character to the addition of nonionic and / or ionic surfactants, promoting increased surface polarity of the polyolefin fiber and therefore greater adhesion with the composite are also described. cementitious.

The quantitative range of surfactant added during the granulation step comprises from 0.1-10% by weight, preferably from 0.1 to 7%, and the quantitative polymer range is from 90.0 to 99.9% by weight.

It is provided in the present invention that the polyolefin used in the polymerization process is a polypropylene homopolymer or ethylene propylene homopolymer or ethylene propylene copolymer or ethylene propylene butene terpolymer or a blend comprising two or more of these components. The polymeric blend can be obtained in both reactor and post reactor.

The polyolefin used is preferably a polypropylene homopolymer consisting only of repetitive units of propylene monomers having a melt index in the range of 2.0 to 40 g / 10min (as determined by the standard that determines the standard test method for melt flow rates of ASTM D-1238 thermoplastics at 230 ° C and 2.16 kg load cell), preferably 4 to 20 g / 10min, most preferably 16 to 20 g / 10min. This homopolymer is obtained via gaseous or liquid phase or slurry polymerization using Ziegler-Natta or metallocene (A) catalyst.

The surfactants may be ionic and / or nonionic.

Ionic surfactants are selected from hexadecyltrimethylammonium derivatives and dodecylamine derivatives and / or mixtures thereof.

Nonionic surfactants are selected from: compounds of the polyester family polyols and must have polar functional groups, allowing for increased interaction between reinforcement fibers and the cementitious matrix. Nonionic surfactants may further comprise compounds of C12 - C18 saturated and unsaturated hydrocarbon chains containing at least one ethylene oxide (EO) unit and one propene oxide (PO) unit up to a maximum of 14EO and 20PO It may further comprise non-ionic triblock copolymers EO / PO / EO (known as Poloxamers) and polyalkylene glycols at concentrations of 0.1-10%. (w / w) during the granulation process in single screw and twin screw extruders.

The increase in surface hydrophilicity is achieved by the addition of lubricants, antistatic agents, surfactants, fatty acid chain compounds, alkoxylated alcohols and their derivatives, and polymers with polar functional groups.

On the other hand, in addition to increasing the surface polarity, these additives (pure or mixed) can also be added to the top oil used in the step prior to fiber stretching, leading to better performance in fiber reinforcing properties.

In a preferred embodiment, the polymeric composition disclosed herein comprises polypropylene, preferably in the form of a porous sphere, added with nonionic surfactants for the purpose of increasing their polarity (surface tension). Additionally, other additives such as antioxidants, nucleating agents, neutralizers, oils, organic and inorganic pigments and mineral fillers may be added to the polypropylene polymer compositions of the present invention.

Granulation of the polypropylene, preferably in the physical form of porous spheres, together with additives described above, preferably occurs in a single or twin screw extruder, under conditions suitable for obtaining a high performance composite reinforcing polypropylene, after obtaining said polymer by polymerization of the base monomer (propene) by the Spheripol process. The process of incorporating the nonionic and / or ionic surfactant in the polypropylene resin occurs in the granulation process, whose surfactant, in pure form, is dosed by a device attached to the extruder directly in the melt or directly in the sphere (wetting) after polymerization process. The resin of the present invention preferably has a melt index of 4 to 20 g / 10 min, more preferably 16 to 20 g / 10 min, toughness in the range of 5 to 15 cN / dtex and chemical binding energy in the range of 1 to 6 J / m2

The present invention is also intended for the production of fiber reinforcing composites whose cross-section is preferably round, not excluding the possibility of being triangular or trilobal. Polypropylene fibers have a high toughness of at least 4 cN / dtex, more preferably at least 7 cN / dtex and particularly 8 to 9 cN / dtex. This range of toughness can be achieved by adjusting the fiber extrusion conditions using the process in an appropriate manner.

The fibers obtained in multifilament extruders are generally in the form of cut fibers having a length in the range of 2 to 20 mm, preferably 8 to 2 mm. The fibers according to the present invention are used as reinforcing agent in fibro-synthetic composites in the proportion of 0.2 to 5% by weight relative to the finished product (composite).

To allow a better understanding of the present invention and to clearly demonstrate the technical advances obtained, the results of Examples 1 and 2 comprising the polymeric compositions disclosed in the present patent application are set forth below.

Example 1: For the preparation of said compositions, the following materials were used:

• Polypropylene: homopolymer of melt index of 18 g / 10min.

• Surfactant 1: 3EO / 6PO ratio lauryl alcohol copolymer, viscosity 45 cP (25 ° C) and density 0.96 g / cm3 (25 ° C).

Table 1 shows the percentage by weight of surfactant added to polypropylene during the granulation step.

Table 1

Examples

1 2

% in large scale

Polypropylene 100 98.5 Surfactant 1 0 1, 5

The pellets thus obtained were processed in a multifilament extruder to obtain polypropylene fibers, which were characterized by pull-out testing, atomic force microscopy (AFM) and mechanical properties, for example, toughness and elongation. The techniques employed for their characterization are as follows:

• Pull-out test: Fiber adhesion in a cementitious matrix was assessed by a laboratory test in which a filament is embedded to a length between 0.5 mm to 2 mm in a formulation that simulates the composite matrix comprised of cement, fillers, sand, water, plasticizers and viscosity modifiers, in the following mass ratios, respectively: 1, 0; 1, 2; 0.8; 0.55; 0.01; 0.001. After 28 days of curing of the matrix, the free end of the filament is subjected to traction, being determined the tensile force and the displacement point. The pull-out test was performed with a 0.1 N load cell and tensile speed from 0.001 to 0.01 mm / min. From the decoupling force versus displacement curve it is possible to determine the chemical bonding energy (Gd) and frictional force (τ) between the fiber and the cementitious composite.

• Surface characterization of fiber by atomic force microscopy (AFM): Surfactant migration to the fiber surface was assessed by AFM Veeco, NanoScope V. The fibers were fixed directly to the sample holder and analyzed using tapping mode. . A 4955J scanner and a silicon-doped antimony single-rod probe with a spring constant of 20 to 80 N / m and an oscillation frequency of 250-299 kHz were used. For fiber surface evaluation, phase variation was monitored, which provides information regarding the electronic density of surface materials and energy dissipation involved in the contact between the tip and the sample. In addition, the contrast difference indicates the level of dissipation, ie darker contrast reveals less dissipation and lower electron density.

· Mechanical properties, toughness and elongation properties were determined according to ASTM D2256 method. Example 2

Example 2 compared to Example 1 shows the effect of surfactant 1 on the mechanical properties of the fiber and its performance in adhesion tests on cementitious composite.

Table 2

The respective results in Table 2 show that the mechanical properties, such as toughness and elongation, and the frictional force (τ) are slightly affected by the presence of nonionic surfactant, but do not compromise its performance. The significant increase in chemical bonding energy (Gd) is observed, which is similar to the performance observed for PVA fiber. These characteristics of the new material make it industrially interesting due to the increased performance of fiber as reinforcement of composites.

Thus, the significant increase in chemical bonding energy (Gd) as observed in Table 2 indicates that there was a significant increase in fiber surface polarity due to the migration of the modifying agents to the fiber surface and subsequent anchoring thereof, thus allowing exposure on said fiber surface. Said fiber surface exposure provides better adhesion to the cementitious composite.

Resin comprising higher polarity obtained by granulation has a melt index preferably from 4 to 20 g / 10 min, more preferably from 16 to 20 g / 10 min, toughness in the range of 5 to 15 cN / dtex and chemical bonding energy in the range of 1 to 6 J / m2.

Figure 1 shows the atomic force microscopy image of pure polypropylene fiber, on which there is a continuous and non-contrasting surface. On the other hand, in Figure 2 it is possible to observe the modification of the fiber surface by the presence of dispersed phase (dark coloration) in the polymer matrix. propylene, showing the migration of surfactants to the fiber surface, thus giving an increase in hydrophilicity (higher polarity). Having described a preferred embodiment example, it should be understood that the scope of the present invention encompasses other possible variations, being limited only by the content of the appended claims, including the possible equivalents thereof.

Claims

1. Polyolefin granulation process, characterized in that it comprises the incorporation of surfactant for the production of polymeric fibers.

Granulation process according to claim 1, characterized in that the polyolefin is selected from: polypropylene homopolymer, polypropylene homopolymer, ethylene propylene copolymer, ethylene propylene butene terpolymer or a blend comprising two or more of these components.

Granulation process according to claim 1, characterized in that the surfactant is in pure form.

Granulation process according to Claim 1, characterized in that the amount of surfactant added is between 0.1 and 10% by weight of resin.

Granulation process according to claim 1, characterized in that the surfactant is ionic and / or nonionic.

Granulation process according to Claim 5, characterized in that the ionic surfactant is selected from hexadecyltrimethylammonium derivatives and dodecylamine derivatives and / or a mixture thereof.

Granulation process according to Claim 5, characterized in that the nonionic surfactant comprises: compounds of C12 - C18 saturated and unsaturated hydrocarbon chains containing at least one unit of ethylene oxide (EO) and one unit of propene oxide (PO) up to a maximum of 14EO and 20PO and may further comprise nonionic triblock EO / PO / EO copolymers (known as Poloxamers) and polyalkylene glycols

8. Polyolefin resin, characterized in that it comprises 1 to 10% by weight of surfactant relative to the mass of the resin.

Resin according to claim 8, characterized in that it has a melt index of 4 to 20 g / 10min, toughness in the range of 5 to 15 cN / dtex and chemical binding energy in the range of 1 to 6 J / m2

Polyolefin resin according to claim 8, characterized in that it is obtained by the process as defined in claims 1 to 7.

Polyolefin fiber, characterized in that it comprises a resin as defined in any one of claims 8 to 10.

12. Use of polyolefin fiber, characterized in that it is used as a reinforcement material in cementitious composites.

Cementitious composite, characterized in that it comprises a fiber as defined in claim 11.

Cementitious composite according to claim 13, characterized in that it comprises 0.2 to 5% by weight of the fiber relative to the mass of the composite.

An invention, characterized by any of its embodiments or claim categories encompassed by the subject matter initially disclosed in the patent application or its examples herein.