WO2022088020A1

WO2022088020A1 - Glass fiber-reinforced composition with flame-retardancy

Info

Publication number: WO2022088020A1
Application number: PCT/CN2020/125176
Authority: WO
Inventors: Xiangyang Zhu; Shengquan ZHU; MaoLin YAN; Feild SHEN
Original assignee: Borouge Compounding Shanghai Co., Ltd.
Priority date: 2020-10-30
Filing date: 2020-10-30
Publication date: 2022-05-05
Also published as: CN117916305A

Abstract

A polyolefin composition (PC) comprising: a) from 40.0 to 60.0 wt. -%of a propylene homopolymer (h-PP) having an MFR ₂ in the range from 5.0 to 49.0 g/10 min; b) from 18.0 to 35.0 wt. -%of flame-retardant (FR); c) from 18.0 to 30.0 wt. -%of glass fibers (GF); d) from 0.1 to 5.0 wt. -%of at least one additive (A) other than the flame-retardant (FR) and the glass fibers (GF), wherein the propylene homopolymer (h-PP) comprises a polymeric nucleating agent.

Description

GLASS FIBER-REINFORCED COMPOSITION WITH FLAME-RETARDANCY

The present invention relates to a polyolefin composition comprising a propylene homopolymer, a flame-retardant, glass fibers, and additives, as well as articles comprising said composition.

The field of electric and hybrid vehicles has developed at an ever-increasing rate over the past decade, driven primarily by the desire to reduce emissions in view of increasingly stringent regulations regarding particle emission in built up areas, but also in view of the desire to limit the contribution to greenhouse gas-promoted climate change. One of the key developments in this field is in the batteries required to enable both longer journeys between charging and improved charging times.

These batteries can be bulky and heavy, housing large quantities of electrolytic solutions. Furthermore, there is the ever-present risk, as in any electric component, of fire. As such, the housing materials for such batteries are required to have highly optimised mechanical properties (primarily a balance of stiffness and impact strength and a higher heat-deflection temperature) , as well as flame-retardancy properties.

Flame-retardants are chemicals used in polymers that inhibit or resist the spread of fire. For improving the flame-retardancy of polymers compositions to be used in wires or cables, compounds containing halides have historically been added to the polymer. These compounds function via the release of relatively stable halogen radicals that are able to quench the radical chain reactions involved in the combustion process. Another approach to achieve high flame-retardant properties in halogen-free polymer compositions has been to add large amounts, typically above 60 wt%of inorganic flame-retardant fillers such as hydrated and hydroxy compounds. Such fillers, which include Al (OH) ₃ and Mg (OH) ₂ decomposes endothermically at temperatures between 200 and 300 ℃, liberating inert gases. The drawback of using large amounts of fillers is the deterioration of the processability and the mechanical properties of the polymer composition. Another group of non-halogenated flame-retardants is the class of organophosphorus. These compounds typically operate by creating a thermal insulation barrier between the burning sections and the unburned plastic, typically a layer of charred phosphoric acid.

As previously alluded to, the addition of large amounts of flame-retardants is known to degrade the mechanical properties and processability of the flame-retardant compositions.

Consequently, new compositions that combine flame-retardant properties with improved mechanical properties (stiffness, impact strength and higher heat-deflection temperature) are required for use in the housing material of electric vehicle storage batteries.

Therefore, the present invention is directed to a polyolefin composition (PC) comprising:

a) from 40.0 to 60.0 wt. -%, based on the total weight of the composition, of a propylene homopolymer (h-PP) having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230 ℃ and 2.16 kg in the range from 5.0 to 49.0 g/10 min;

b) from 18.0 to 35.0 wt. -%, based on the total weight of the composition, of a flame-retardant (FR) ;

c) from 18.0 to 30.0 wt. -%, based on the total weight of the composition, of glass fibers (GF) ; and

d) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the flame-retardant (FR) and the glass fibers (GF) ,

wherein the propylene homopolymer (h-PP) comprises a polymeric nucleating agent.

In a preferred embodiment, the polymeric nucleating agent is a vinyl cycloalkane polymer, preferably vinyl cyclohexane polymer, most preferably a vinyl cyclohexane homopolymer.

In another preferred embodiment, the propylene homopolymer (h-PP) has one or more, preferably all, of the following properties:

i) a xylene cold solubles (XCS) content in the range from 0.5 to 3.0 wt. -%, preferably in the range from 0.7 to 2.0 wt. -%, most preferably in the range from 0.9 to 1.7 wt. -%;

ii) a melting temperature, measured by DSC analysis, in the range from 160 to 169 ℃, more preferably in the range from 161 to 168 ℃, most preferably in the range from 162 to 168 ℃;

iii) a flexural modulus, measured according to according to ISO 178 on 80x10x4 mm ³ test bars injection molded in line with EN ISO 1873-2, in the range from 1000 to 3000 MPa, more preferably in the range from 1500 to 2500 MPa, most preferably in the range from 1800 to 2200 MPa;

iv) a Vicat softening temperature, measured according to ISO 306 (A50) at a load of 10 N and a heating rate of 50 K/h, in the range from 150 to 165 ℃, more preferably in the range from 153 to 162 ℃, most preferably in the range from 155 to 160 ℃; and

v) a Charpy notched impact strength, measured at 23 ℃ according to ISO 179-1 1eA using injection-molded bar test specimens of 80x10x4 mm3 prepared in accordance with ISO 1873-2: 2007, in the range from 1.0 to 10.0 kJ/m ², more preferably in the range from 2.0 to 7.0 kJ/m ², most preferably in the range from 2.5 to 5.0 kJ/m ².

In another preferred embodiment, the flame-retardant (FR) is a non-halogenated flame-retardant, more preferably a non-halogenated organophosphorus flame-retardant, most preferably selected from piperazine pyrophosphate, melamine polyphosphate, calcium bis (dihydrogenorthophosphate) , calcium hydrogen phosphonate and mixtures thereof.

In another preferred embodiment, the glass fibers (GF) are chopped glass fibers, more preferably chopped glass fibers with a nominal diameter in the range from 5 to 30 μm, preferably in the range from 7 to 20 μm, most preferably in the range from 10 to 15 μm, and/or a chop length in the range from 1.0 to 10.0 mm, more preferably in the range from 2.0 to 7.0 mm, most preferably in the range from 3.0 to 5.0 mm

In another preferred embodiment, the polyolefin composition (PC) further comprises:

e) from 0.1 to 2.5 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) , preferably a maleic anhydride-modified polypropylene.

In a further preferred embodiment, the polar modified polypropylene (PMP) has a polar group loading in the range from 0.5 to 3.0 wt. -%.

In another preferred embodiment, the polyolefin composition (PC) has a flexural modulus of at least 4500 MPa, and/or a Charpy notched impact strength at 23 ℃ of at least 5.0 kJ/m ².

In another preferred embodiment, the polyolefin composition (PC) has a heat deflection temperature, measured according to ISO 75-2 under a load of 1.8 MPa, in the range from 140 to 160 ℃.

In another preferred embodiment, the polyolefin composition (PC) has a flame-retardancy classification, as measured according to test standard UL94-2013, of V-0.

In another aspect, the present invention is directed to a process for the preparation of said polyolefin composition (PC) , comprising the steps of:

a) providing at least one additive (A) , preferably in the form of a master batch;

b) providing a propylene homopolymer (h-PP) and an optional polar-modified polypropylene (PMP) ;

c) providing a flame-retardant (FR) ;

d) providing glass fibers (GF) ; and

e) blending and extruding the propylene homopolymer (h-PP) with the at least one additive (A) , the flame-retardant (FR) and the glass fiber (GF) at a temperature in the range from 120 ℃ to 250 ℃ in an extruder, preferably a twin-screw extruder.

In a further aspect, the present invention is directed to an article comprising more than 75 wt. -%of the polyolefin composition (PC) , preferably a molded article, most preferably an injection molded article.

In a preferred embodiment, the article is an automotive article, preferably the article is the housing for a storage battery in an electric vehicle.

The present invention will now be described in more detail.

The propylene homopolymer (h-PP)

The main component of the polyolefin composition is the propylene homopolymer (h-PP) .

The propylene homopolymer (h-PP) of the present invention has a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃ and 2.16 kg in the range from 5.0 to 49.0 g/10 min, preferably in the range from 6.0 to 40.0 g/10 min, more preferably in the range from 7.0 to 30.0 g/10 min, yet more preferably in the range from 7.5.0 to 20.0 g/10 min, most preferably in the range from 8.0 to 15.0 g/10 min.

It is preferred that the propylene homopolymer (h-PP) of the present invention has a xylene cold solubles (XCS) content in the range from 0.5 to 3.0 wt. -%, preferably in the range from 0.7 to 2.0 wt. -%, most preferably in the range from 0.9 to 1.7 wt. -%.

It is preferred that the propylene homopolymer (h-PP) of the present invention has a melting temperature, measured by DSC analysis, in the range from 160 to 169 ℃, more preferably in the range from 161 to 168 ℃, most preferably in the range from 162 to 168 ℃.

It is preferred that the propylene homopolymer (h-PP) of the present invention has a flexural modulus measured according to ISO 178 in the range from 1000 to 3000 MPa, more preferably from 1500 to 2500 MPa, most preferably from 1800 to 2200 MPa.

It is preferred that the propylene homopolymer (h-PP) of the present invention has a Vicat softening temperature, measured according to ISO 306 (A50) at a load of 10 N and a heating rate of 50 K/h, in the range from 150 to 165 ℃, more preferably in the range from 153 to 162 ℃, most preferably in the range from 155 to 160 ℃.

It is preferred that the propylene homopolymer (h-PP) of the present invention has a Charpy Notched Impact Strength measured according to ISO 179/1eA at 23 ℃ in the range from 1.0 to 10.0 kJ/m ², more preferably in the range from 2.0 to 7.0 kJ/m ², most preferably from 2.5 to 5.0.0 kJ/m ².

The propylene homopolymer (h-PP) must comprise a polymeric nucleating agent.

A preferred example of such a polymeric nucleating agent is a vinyl polymer, such as a vinyl polymer derived from monomers of the formula

CH ₂ = CH-CHR ¹R ²

wherein R ¹ and R ², together with the carbon atom they are attached to, form an optionally substituted saturated or unsaturated or aromatic ring or a fused ring system, wherein the ring or fused ring moiety contains four to 20 carbon atoms, preferably 5 to 12 membered saturated or unsaturated or aromatic ring or a fused ring system or independently represent a linear or branched C4-C30 alkane, C4-C20 cycloalkane or C4-C20 aromatic ring. Preferably R ¹ and R ², together with the C-atom wherein they are attached to, form a five-or six-membered saturated or unsaturated or aromatic ring or independently represent a lower alkyl group comprising from 1 to 4 carbon atoms. Preferred vinyl compounds for the preparation of a polymeric nucleating agent to be used in accordance with the present invention are in particular vinyl cycloalkanes, in particular vinyl cyclohexane (VCH) , vinyl cyclopentane, and vinyl-2-methyl cyclohexane, 3-methyl-1-butene, 3-ethyl-1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene or mixtures thereof. It is particularly preferred that the vinyl polymer is a vinyl cycloalkane polymer, preferably selected from vinyl cyclohexane (VCH) , vinyl cyclopentane and vinyl-2-methyl cyclohexane, with vinyl cyclohexane polymer being a particularly preferred embodiment.

It is further preferred that the vinyl polymer of the polymeric nucleating agent is a homopolymer, most preferably a vinyl cyclohexane homopolymer.

The propylene homopolymer (h-PP) of the present invention may either be synthesized or selected from commercially available polypropylenes.

The flame-retardant (FR)

As another essential component, the polyolefin composition (PC) comprises flame-retardant (FR) .

The skilled person would understand that the term flame-retardant refers to any compound typically used in the art for improving the flame-retardant properties of polyolefin compositions.

Said flame-retardant (FR) may either be a halogenated flame-retardant or a non-halogenated flame-retardant. Preferably, the flame-retardant (FR) is a non-halogenated flame-retardant.

Typical halogenated flame-retardants include organohalogen compounds, selected from organochlorines such as chlorendic acid derivatives and chlorinated paraffins; organobromines such as decabromodiphenyl ether (decaBDE) , decabromodiphenyl ethane (a replacement for decaBDE) , polymeric brominated compounds such as brominated polystyrenes, brominated carbonate oligomers (BCOs) , brominated epoxy oligomers (BEOs) , tetrabromophthalic anyhydride, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) ;

in combination with inorganic synergists, such as antimony pentoxide, sodium antimonite and antimony trioxide.

If the flame-retardant of the present invention is a halogenated flame-retardant, then it is preferably selected from the above list or mixtures of the flame-retardants from the above list. In one embodiment the halogenated flame-retardant would be a mixture of decabromodiphenyl ethane and antimony trioxide.

Typical non-halogenated flame-retardants include minerals such as aluminium hydroxide (ATH) , magnesium hydroxide (MDH) , huntite and hydromagnesite, red phosphorus and borates, as well as organophosphorus compounds including ammonium polyphosphate, melamine polyphosphate, triphenyl phosphate (TPP) , resorcinol bis (diphenylphosphate) (RDP) , bisphenol A diphenyl phosphate (BADP) , tricresyl phosphate (TCP) , dimethyl methylphosphonate (DMMP) , aluminium diethyl phosphinate, piperazine pyrophosphate, melamine pyrophosphate, calcium bis (dihydrogenorthophosphate) and calcium hydrogen phosphonate. These flame-retardants can be used alone or in the form of a mixture.

The flame-retardant of the present invention is preferably a non-halogenated flame-retardant, more preferably a non-halogenated organophosphorus flame-retardant, most preferably selected from piperazine pyrophosphate, melamine polyphosphate, calcium bis (dihydrogenorthophosphate) , calcium hydrogen phosphonate and mixtures thereof.

One suitable commercially available non-halogenated flame-retardant is Amgard PP1, available from Solvay S.A. (China) .

The glass fibers (GF)

Another essential component of the polyolefin composition (PC) is the glass fibers (GF) .

The glass fibers are preferably provided in the form of chopped glass fibers.

It is preferred that the chopped glass fibers have a nominal diameter in the range from 5 to 30 μm, preferably in the range from 7 to 20 μm, most preferably in the range from 10 to 15 μm.

It is also preferred that the chopped glass fibers have a chop length in the range from 1.0 to 10.0 mm, more preferably in the range from 2.0 to 7.0 mm, most preferably in the range from 3.0 to 5.0 mm.

The additives (A)

The polyolefin composition (PC) of the present invention may contain additives (A) in an amount of from 0.1 to 5.0 wt. -%. The skilled practitioner would be able to select suitable additives that are well known in the art.

The additives (A) are preferably selected from antioxidants, UV-stabilisers, anti-scratch agents, mold release agents, acid scavengers, lubricants, anti-static agents, colorant or pigment, and mixtures thereof.

It is understood that the content of additives (A) , given with respect to the total weight of the polyolefin composition (PC) , includes any carrier polymers used to introduce the additives to said polyolefin composition (PC) , i.e. masterbatch carrier polymers. An example of such a carrier polymer would be a polypropylene homopolymer in the form of powder.

The polar modified polypropylene (PMP)

In certain preferred embodiments, the polyolefin composition (PC) of the invention may further comprise a polar-modified polypropylene (PMP) .

Whilst not wishing to be bound by any theory, it is believed that the polar-modified polypropylene (PMP) is used as a compatibilizer in the composition, which further helps to disperse the glass fibers within the polyolefin composition (PC) .

It is preferred that the polar-modified polypropyplene (PMP) has a content of polar groups content in the range from 0.5 to 3.0 wt. -%, more preferably in the range from 0.7 to 2.0 wt. -%, most preferably in the range from 0.8 to 1.5 wt. -%.

It is also preferred that the polar-modified polypropylene (PMP) has a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃ and 2.16 kg in the range from 30.0 to 150.0 g/10 min, more preferably in the range from 40.0 to 120.0 g/10 min, most preferably in the range from 50.0 to 100.0 g/10 min.

It is especially preferred that the polar-modified polypropylene (PMP) is a maleic anhydride-modified polypropylene.

Suitable commercially available polar-modified polypropylenes include CMG5701, available from Fine-Blend Compatibilizer Jiangsu Co., Ltd. (China) .

The polyolefin composition

The polyolefin composition of the present invention comprises several essential components, including the propylene homopolymer (h-PP) , the flame-retardant (FR) , the glass fibers (GF) , and the at least one additive (A) other than the flame-retardant (FR) and the glass fibers (GF) . Accordingly the polyolefin composition (PC) comprises:

d) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the flame-retardant (FR) and the glass fibers (GF) .

The polyolefin composition (PC) may further comprise:

e) from 0.1 to 2.5 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

The polyolefin composition (PC) of the present invention can comprise further components, in addition to the essential components as defined above. However, it is preferred that the individual contents of the propylene homopolymer (h-PP) , the flame-retardant (FR) , the glass fibers (GF) , and the at least one additive (A) and the optional polar-modified polypropylene (PMP) add up to at least 90 wt. -%, more preferably to at least 95 wt. -%, based on the total weight of the polyolefin composition (PC) . Most preferably the polyolefin composition (PC) consists of only the propylene homopolymer (h-PP) , the flame-retardant (FR) , the glass fibers (GF) , and the at least one additive (A) and the optional polar-modified polypropylene (PMP) .

The propylene homopolymer (h-PP) is present in the polyolefin composition in an amount of from 40.0 to 60.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 40.0 to 54.0 wt. -%, most preferably in an amount from 43.0 to 53.0 wt. -%, based on the total weight of the composition.

The flame-retardant (FR) is present in the polyolefin composition in an amount of from 18.0 to 35.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 22 to 33.0 wt. -%, most preferably in an amount of from 22.0 to 30.0 wt. -%based on the total weight of the composition.

The glass fibers (GF) are present in the polyolefin composition in an amount of from 18.0 to 30.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 19.0 to 27.0 wt. -%, most preferably in an amount of from 20.0 to 24.0 wt. -%based on the total weight of the composition.

If present, it is preferred that the polar-modified polypropylene (PMP) is present in the polyolefin composition in an amount of from 0.1 to 2.5 wt. -%, based on the total weight of the composition, more preferably in an amount of from 0.3 to 2.0 wt. -%, most preferably in an amount of from 0.5 to 1.5 wt. -%based on the total weight of the composition.

Accordingly, in one preferred embodiment, the polyolefin composition (PC) comprises, preferably consists of:

c) from 18.0 to 30.0 wt. -%, based on the total weight of the composition, of glass fibers (GF) ;

d) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the flame-retardant (FR) and the glass fibers (GF) ; and

e) optionally from 0.1 to 2.5 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

Accordingly, in a further preferred embodiment, the polyolefin composition (PC) comprises, preferably consists of:

a) from 40.0 to 54.0 wt. -%, based on the total weight of the composition, of a propylene homopolymer (h-PP) having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230 ℃ and 2.16 kg in the range from 5.0 to 49.0 g/10 min;

b) from 22.0 to 33.0 wt. -%, based on the total weight of the composition, of a flame-retardant (FR) ;

c) from 19.0 to 27.0 wt. -%, based on the total weight of the composition, of glass fibers (GF) ;

d) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the flame-retardant (FR) and the glass fibers (GF) ;

e) optionally from 0.3 to 2.0 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

Accordingly, in yet another preferred embodiment, the polyolefin composition (PC) comprises, preferably consists of:

a) from 43.0 to 53.0 wt. -%, based on the total weight of the composition, of a propylene homopolymer (h-PP) having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230 ℃ and 2.16 kg in the range from 5.0 to 49.0 g/10 min;

b) from 22.0 to 30.0 wt. -%, based on the total weight of the composition, of a flame-retardant (FR) ;

c) from 20.0 to 24.0 wt. -%, based on the total weight of the composition, of glass fibers (GF) ;

e) optionally from 0.5 to 1.5 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

In order to be suitable for use in housing storage batteries in electric vehicles, the polyolefin composition (PC) according to the present invention requires beneficial mechanical properties, such as stiffness and impact strength, and heat-deflection temperature, in addition to good flame and heat resistance properties.

Accordingly, it is preferred that the polyolefin composition (PC) has a flexural modulus measured according to ISO 178 of at least 5000 MPa, more preferably of at least 6000 MPa, most preferably of at least 6500 MPa.

The flexural modulus will not typically exceed 8000 MPa

It is also preferred that the polyolefin composition (PC) has an Izod notched impact strength measured according to ISO 180 at +23℃ of at least 5.0 kJ/m ², more preferably of at least 6.0 kJ/m ², most preferably of at least 7.0 kJ/m ².

The Izod notched impact strength will not typically exceed 20.0 kJ/m ².

Preferably, the polyolefin composition (PC) has a heat deflection temperature, measured according to ISO 75-2 under a load of 1.8 MPa, in the range from 140 to 160 ℃, more preferably in the range from 143 to 155 ℃, most preferably in the range from 145 to 150 ℃.

Additionally, it is preferred that the polyolefin compositions (PC) has a flame-retardancy classification, as measured according to test standard UL94-2013, of V-0.

Preparation process for the propylene homopolymer (h-PP)

The propylene homopolymer (h-PP) comprised in the composition according to this invention is preferably produced in a sequential polymerization process in the presence of a Ziegler-Natta catalyst, more preferably in the presence of a catalyst (system) as defined below.

Preferably, the process for the preparation of the polypropylene is a process for the production of a propylene homopolymer.

The term “polymerization reactor” shall indicate that the main polymerization takes place. Thus in case the process consists of two polymerization reactors, this definition does not exclude the option that the overall process comprises for instance a pre-polymerization step in a pre-polymerization reactor before the two polymerization reactors. The term “consist of” is only a closing formulation in view of the main polymerization reactors, i.e. does not exclude prepolymerisation reactors prior to said main polymerization reactors.

Preferably, said process comprises the steps of

(a1) polymerizing propylene in a first reactor (R1) obtaining a first propylene homopolymer fraction (h-PP1) ;

(b1) transferring the first propylene homopolymer fraction (h-PP1) in a second reactor (R2) ; and

(c1) polymerizing in the second reactor (R2) , in the presence of said first propylene homopolymer fraction (PP1) , propylene obtaining thereby the second propylene homopolymer fraction (h-PP2) , the first propylene homopolymer fraction (h-PP1) and the second propylene homopolymer fraction (h-PP2) together forming the propylene homopolymer (h-PP) .

The first reactor (R1) is preferably a slurry reactor (SR) and can be any continuous or simple stirred batch tank reactor or loop reactor operating in bulk or slurry. Bulk means a polymerization in a reaction medium that comprises of at least 60 % (w/w) monomer. According to the present invention the slurry reactor (SR) is preferably a (bulk) loop reactor (LR) .

The second reactor (R2) is preferably a gas phase reactor (GPR) . Such a gas phase reactor (GPR) can be any mechanically mixed or fluid bed reactors. Preferably the gas phase reactor (GPR) comprises a mechanically agitated fluid bed reactor with gas velocities of at least 0.2 m/sec. Thus, it is appreciated that the gas phase reactor is a fluidized bed type reactor preferably with a mechanical stirrer.

Thus in a preferred embodiment the first reactor (R1) is a slurry reactor (SR) , like loop reactor (LR) , whereas the second reactor (R2) is a gas phase reactor (GPR) . Accordingly for the instant process at least two, preferably two polymerization reactors, namely a slurry reactor (SR) , like loop reactor (LR) , and a gas phase reactor (GPR) connected in series are used. If needed prior to the slurry reactor (SR) a pre-polymerization reactor is placed.

A preferred multistage process is a “loop-gas phase” -process, such as developed by Borealis A/S, Denmark (known as

technology) described e.g. in patent literature, such as in EP 0 887 379, WO 92/12182 WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 or in WO 00/68315.

A further suitable slurry-gas phase process is the

process of Basell described e.g. in figure 20 of the paper by Galli and Vecello, Prog. Polym. Sci. 26 (2001) 1287-1336.

Preferably, in the instant process for producing the propylene homopolymer (h-PP) as defined above the conditions for the first reactor (R1) , i.e. the slurry reactor (SR) , like a loop reactor (LR) , of step (a1) may be as follows:

- the temperature is within the range of 40 ℃ to 110 ℃, preferably between 60 ℃ and 100 ℃, like 68 to 95 ℃,

- the pressure is within the range of 20 bar to 80 bar, preferably between 40 bar to 70 bar,

- hydrogen can be added for controlling the molar mass in a manner known per se.

Subsequently, the reaction mixture from step (a1) containing preferably the first propylene homopolymer fraction (h-PP1) is transferred to the second reactor (R2) , i.e. the gas phase reactor (GPR) , whereby the conditions are preferably as follows:

- the temperature is within the range of 50 ℃ to 130 ℃, preferably between 60 ℃ and 100 ℃,

- the pressure is within the range of 5 bar to 50 bar, preferably between 15 bar to 35 bar,

If desired, the polymerization may be effected in a known manner under supercritical conditions in the first reactor (R1) , i.e. in the slurry reactor (SR) , like in the loop reactor (LR) , and/or as a condensed mode in the gas phase reactor (GPR-1) .

The residence time can vary in the above different reactors.

In one embodiment of the process for producing the propylene copolymer the residence time the first reactor (R1) , i.e. the slurry reactor (SR) , like a loop reactor (LR) , is in the range 0.2 to 4 hours, e.g. 0.3 to 1.5 hours and the residence time in the gas phase reactor (GPR) will generally be 0.2 to 6.0 hours, like 0.5 to 4.0 hours.

In the process of the invention a well-known prepolymerization step may precede before the actual polymerization in the reactors (R1) to (R2) . The prepolymerisation step is typically conducted at a temperature of 0 to 50 ℃, preferably from 10 to 45 ℃, and more preferably from 15 to 40 ℃.

More preferably the propylene homopolymer (h-PP) is obtained in the presence of:

(I) a solid catalyst component comprising a magnesium halide, a titanium halide and an internal electron donor; and

(II) a cocatalyst comprising an aluminium alkyl and optionally an external electron donor, and

(III) an optional nucleating agent, preferably in the presence of a nucleating agent as defined above or below;

and in a sequential polymerization process as defined in the present invention.

It is especially preferred that the process according to the present invention includes the following process steps:

polymerizing a vinyl compound as defined above, preferably vinyl cyclohexane (VCH) , in the presence of a catalyst system comprising the solid catalyst component to obtain a modified catalyst system which is the reaction mixture comprising the solid catalyst system and the produced polymer of the vinyl compound, preferably, and wherein, the weight ratio (g) of the polymer of the vinyl compound to the solid catalyst system is up to 5 (5: 1) , preferably up to 3 (3: 1) most preferably is from 0.5 (1: 2) to 2 (2: 1) , and the obtained modified catalyst system is fed to polymerization step (a1) of the process for producing the propylene homopolymer (h-PP) .

The used catalyst is preferably a Ziegler-Natta catalyst system and even more preferred a modified Ziegler Natta catalyst system as defined in more detail below.

Such a Ziegler-Natta catalyst system typically comprises a solid catalyst component, preferably a solid transition metal component, and a cocatalyst, and optionally an external donor. The solid catalyst component comprises most preferably a magnesium halide, a titanium halide and an internal electron donor. Such catalysts are well known in the art. Examples of such solid catalyst components are disclosed, among others, in WO 87/07620, WO 92/21705, WO 93/11165, WO 93/11166, WO 93/19100, WO 97/36939, WO 98/12234, WO 99/33842.

Suitable electron donors are, among others, esters of carboxylic acids, like phthalates, citraconates, and succinates. Also oxygen-or nitrogen-containing silicon compounds may be used. Examples of suitable compounds are shown in WO 92/19659, WO 92/19653, WO 92/19658, US 4,347,160, US 4,382,019, US 4,435,550, US 4,465,782, US 4,473,660, US 4,530,912 and US 4,560,671.

Moreover, said solid catalyst components are preferably used in combination with well known external electron donors, including without limiting to, ethers, ketones, amines, alcohols, phenols, phosphines and silanes, for example organosilane compounds containing Si-OCOR, Si-OR, or Si-NR ₂ bonds, having silicon as the central atom, and R is an alkyl, alkenyl, aryl, arylalkyl or cycloalkyl with 1-20 carbon atoms; and well known cocatalysts, which preferably comprise an aluminium alkyl compound as known in the art, to polymerise the propylene copolymer.

When a nucleating agent is introduced to the propylene homopolymer (h-PP) during the polymerisation process of the propylene copolymer, the amount of nucleating agent present in the propylene homopolymer (h-PP) is preferably not more than 500 ppm, more preferably is 0.025 to 200 ppm, still more preferably is 1 to 100 ppm, and most preferably is 5 to 100 ppm, based on the propylene homopolymer (h-PP) and the nucleating agent, preferably based on the total weight of the propylene homopolymer (h-PP) including all additives.

The process for preparing the polyolefin composition (PC)

The present invention is additionally directed to a process for the preparation of the polyolefin composition (PC) of the present invention, comprising the steps of:

c) providing a flame-retardant (FR) ;

d) providing glass fibers (GF) ;

In particular, it is preferred to use a conventional compounding or blending apparatus, e.g. a Banbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin-screw extruder. More preferably, mixing is accomplished in a co-rotating twin-screw extruder. The polymer materials recovered from the extruder are usually in the form of pellets. These pellets are then preferably further processed, e.g. by compression molding to generate articles and products of the inventive polyolefin composition (PC) .

The article

The present invention also relates to articles comprising the polyolefin composition (PC) of the invention.

Preferably the article of the invention comprises more than 75 wt. -%of the polyolefin composition (PC) , more preferably more than 85 wt. -%, yet more preferably more than 90 wt. -%, most preferably more than 95 wt. -%of the of the polyolefin composition (PC) .

The article is preferably a molded article, most preferably an injection molded article.

Preferably the article is an automotive article, more preferably the article is the housing for a storage battery in an electric vehicle.

EXAMPLES

1. Definitions/Measuring Methods

The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

Melting temperature Tm is measured according to ISO 11357-3.

MFR ₂: The melt flow rate (MFR) is determined according to ISO 1133 and is indicated in g/10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR ₂ of polypropylene is determined at a temperature of 230 ℃ and a load of 2.16 kg.

Maleic anhydride content: FT-IR standards are prepared by blending a PP homopolymer with different amounts of MAH to create a calibration curve (absorption/thickness in cm versus MAH content in weight %) . The MAH content is determined in the solid-state by IR spectroscopy using a Bruker Vertex 70 FTIR spectrometer on 25x25 mm square films of 100 μm thickness (with an accuracy of ± 1 μm) prepared by compression molding at 190 ℃ with 4 -6 mPa clamping force. Standard transmission FTIR spectroscopy is employed using a spectral range of 4000-400 cm ^-1, an aperture of 6 mm, a spectral resolution of 2 cm ^-1, 16 background scans, 16 spectrum scans, an interferogram zero filling factor of 32 and Norton Beer strong apodisation.

At the adsorption band peak of 1787 cm ^-1 MAH is measured. For the calculation of the MAH content the range between 1830-1727 cm ^-1 is evaluated (after a base line correction) following the calibration standard curve.

The xylene soluble fraction (XCS) at room temperature (XCS, wt. -%) : The amount of the polymer soluble in xylene is determined at 25 ℃ according to ISO 16152; first edition; 2005-07-01. The remaining part is the xylene cold insoluble (XCU) fraction.

Charpy impact test: The Charpy notched impact strength (NIS) was measured according to ISO 179-1 eA at +23 ℃, using injection-molded bar test specimens of 80x10x4 mm3 prepared in accordance with ISO 1873-2: 2007.

Izod impact test: The Izod notched impact strength (NIS) was measured according to EN ISO 180 at +23 ℃, using injection-molded bar test specimens of 80x10x4 mm3 prepared in accordance with ISO 1873-2: 2007.

Flexural Modulus and Flexural Strength: The flexural modulus and flexural strength were determined in 3-point-bending at 23 ℃ according to ISO 178 on 80x10x4 mm ³ test bars injection molded in line with EN ISO 1873-2.

The Heat Deflection Temperature (HDT) is determined according to ISO 75-2 Method A (load 1.80 MPa surface stress) using a Ceast 6921 of

GmbH, Germany.

The Vicat Softening Temperature (Vicat A50) is determined according to ISO 306 (A50) at a load of 10 N and a heating rate of 50 K/h, using a Ceast 6921 of

GmbH, Germany. The Viact A is the temperature at which the specimen is penetrated to a depth of 1 mm by a flat-ended needle with a 1 mm ² circular or square cross-section, under a 1000 gm load.

Flame-retardancy test: The flame-retardant properties of the compositions were tested according to standard UL94-2013.

Before testing, the specimens must be conditioned. Such conditioning requires to maintain the specimens at 23℃ and 50%relative humidity for at least 48 hours prior to the test.

A specimen with a size of 125mm (length) *13mm (width) *1.5 mm (thickness) is used in the test. One end of the specimen is held by a clamp and the other end is free, and the specimen hangs vertically down.

A burner flame is applied to the free end of the specimen for the first 10 seconds, and then taken away. After the flame of the specimen goes out (if any) , the burner flame is applied again to the free end of the specimen for the second 10 seconds, and then taken away. One set of 5 specimens is tested. In addition, a small mass of cotton batt is placed under the flaming specimen during the test. The test results are recorded for each specimen as follows:

■ Duration of the flaming combustion time after the first 10 sec. application of burner flame.

■ Duration of the flaming combustion time after the second 10 sec. application of burner flame.

■ Duration of the glowing combustion time after the second 10 sec. application of burner flame.

■ Whether or not the flaming drippings ignite the cotton placed under the specimen.

■ Whether or not the specimen burns up to the holding clamp.

The rating standard of the test result is listed in Table 1 below:

Table 1: the rating standard of flame-retardancy classes V-0 to V-2

The major difference between class V-1 and V-2 is whether the flaming drippings ignite the cotton placed under the specimen. For polypropylene based material, it is very easy to change from class V-0 to V-2 (no transition state of class V-1) , because the flaming drippings of polypropylene very easily ignite the cotton.

2. Examples

2.1. Synthesis of polypropylene (PP1)

The catalyst used in the polymerizations was a Ziegler-Natta catalyst from Borealis having Ti-content of 1.9 wt. -% (as described in EP 591 224) . Before the polymerization, the catalyst was prepolymerized with vinyl-cyclohexane (VCH) as described in EP 1 028 984 and EP 1 183 307. The ratio of VCH to catalyst of 1: 1 was used in the preparation, thus the final Poly-VCH content was less than 100 ppm. In the first stage the catalyst described above was fed into prepolymerization reactor together with propylene and small amount of hydrogen (2.5 g/h) and ethylene (330 g/h) . Triethylaluminium as a cocatalyst and dicyclopentyldimethoxysilane as a donor was used. The aluminium to donor ratio was 7.5 mol/mol and aluminium to titanium ratio was 300 mol/mol. Reactor was operated at a temperature of 30 ℃and a pressure of 55 barg.

The subsequent polymerization has been effected under the following conditions.

Table 2: Polymerization conditions for PP1

2.2. Compounding of examples

The propylene compositions of Inventive examples IE1 to IE3 and comparative examples CE1 were prepared based on the recipes indicated in Table 3 by compounding in a co-rotating twin-screw extruder under the conditions described in Table 4. The extruder has 12 heating zones.

Table 3: Recipes for Comparative and Inventive examples

PP2 propylene homopolymer having a melt flow rate of 7.0 g/10 min, which is not nucleated with pVCH.

PMP maleic anhydride-grafted polypropylene with a trade name of CMG5701, available from Fine-Blend Compatibilizer Jiangsu Co., Ltd (China) , having a grafted maleic anhydride content of 1.0 wt. -%.

FR1 flame-retardant with a trade name of Amgard PP1, available from Solvay S. A. (China) , comprising 20%piperazine pyrophosphate, 20%melamine polyphosphate, 30%calcium bis(dihydrogenorthophosphate) , and 30%calcium hydrogen phosphonate.

FR2 a mixture of 70%decabromodiphenyl ethane (CAS-no. 84852-53-9) and 30%antimony trioxide (CAS-no. 1309-64-4) .

GF chopped strand glass fibers with a trade name of CS 248A-13P, available from Owens Corning Composites (China) , having nominal diameter of 13 μm and a chop length of 4.0 mm.

A an additive masterbatch, consisting of 0.8 wt. -%of a carrier propylene homopolymer with a trade name of PP-H 225, available from Hongji petrochemical (China) , having an MFR ₂ (230 ℃, 2.16 kg) of 27 g/10 min, 0.6 wt. -%of a heat stabilizer with a trade name of Irganox PS 802 FL (CAS-no. 693-36-7) , available from BASF SE (Germany) , 0.3 wt. -%of an antioxidant with a trade name of Irganox 3114 (CAS-no. 27676-62-6) , available from BASF SE (Germany) , 0.2 wt. -%of an antioxidants with a trade name of Irgafos 168 (CAS-no. 31570-04-4) , available from BASF SE (Germany) , and 0.1 wt. -%of calcium stearate (CAS-no. 1592-23-0) , available from FACI Chemicals (Zhangjiagang) Co., Ltd (China) .

CMB a colour masterbatch with a trade name TP90002452BG, available from PolyOne (Shanghai) Co., Ltd (China) .

Table 4: Compounding conditions for Inventive examples in a twin-screw extruder

Table 5: Properties of comparative and inventive examples

As can be seen from the examples in Table 5, the inventive examples display drastically improved stiffness with both the flexural modulus and flexural strength being much higher for IE1 to IE3 than for CE1. Furthermore, the heat deflection temperature of all three inventive examples is at least 10 ℃ higher than that of CE1.

It can be further seen that the advantageous stiffness and heat deflection temperature can be improved further by decreasing the amount of flame-retardant in favour of more of the base polypropylene. This does, however come at the price of reduced flame-retardancy, with the flame-retardancy of IE3 falling outside the V0 classification that would be required for applications involving high flame-retardancy, making the composition of IE3 less suitable for these highly specialised applications (although still applicable to many less specialised applications) .

As discussed in the measurement methods, no compositions having V1 flame-retardancy were observed, due to the ease with which molten polypropylene ignites the cotton of the flame-retardancy test.

The high flame-retardancy of IE1 and IE2, combined with their impressive balance of mechanical properties (especially stiffness and heat deflection temperature) make them excellent candidates for use in the housing material of storage batteries in electric cars.

Claims

A polyolefin composition (PC) comprising:

a) from 40.0 to 60.0 wt. -%, based on the total weight of the composition, of a propylene homopolymer (h-PP) having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230 ℃ and 2.16 kg in the range from 5.0 to 49.0 g/10 min;

b) from 18.0 to 35.0 wt. -%, based on the total weight of the composition, of a flame-retardant (FR) ;

c) from 18.0 to 30.0 wt. -%, based on the total weight of the composition, of glass fibers (GF) ; and

d) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the flame-retardant (FR) and the glass fibers (GF) ,

wherein the propylene homopolymer (h-PP) comprises a polymeric nucleating agent .
The polyolefin composition (PC) according to claim 1, wherein the polymeric nucleating agent is a vinyl cycloalkane polymer, preferably vinyl cyclohexane polymer, most preferably a vinyl cyclohexane homopolymer.
The polyolefin composition (PC) according to claim 1 or 2, wherein the propylene homopolymer (h-PP) has one or more, preferably all, of the following properties:

i) a xylene cold solubles (XCS) content in the range from 0.5 to 3.0 wt. -%, preferably in the range from 0.7 to 2.0 wt. -%, most preferably in the range from 0.9 to 1.7 wt. -%;

ii) a melting temperature, measured by DSC analysis, in the range from 160 to 169 ℃, more preferably in the range from 161 to 168 ℃, most preferably in the range from 162 to 168 ℃;

iii) a flexural modulus, measured according to according to ISO 178 on 80x10x4 mm ³ test bars injection molded in line with EN ISO 1873-2, in the range from 1000 to 3000 MPa, more preferably in the range from 1500 to 2500 MPa, most preferably in the range from 1800 to 2200 MPa;

iv) a Vicat softening temperature, measured according to ISO 306 (A50) at a load of 10 N and a heating rate of 50 K/h, in the range from 150 to 165 ℃, more preferably in the range from 153 to 162 ℃, most preferably in the range from 155 to 160 ℃; and

v) a Charpy notched impact strength, measured at 23 ℃ according to ISO 179-1 1eA using injection-molded bar test specimens of 80x10x4 mm ³ prepared in accordance with ISO 1873-2: 2007, in the range from 1.0 to 10.0 kJ/m ², more preferably in the range from 2.0 to 7.0 kJ/m ², most preferably in the range from 2.5 to 5.0 kJ/m ².
The polyolefin composition (PC) according to any one of the preceding claims, wherein the flame-retardant (FR) is a non-halogenated flame-retardant, more preferably a non-halogenated organophosphorus flame-retardant, most preferably selected from piperazine pyrophosphate, melamine polyphosphate, calcium bis (dihydrogenorthophosphate) , calcium hydrogen phosphonate and mixtures thereof.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the glass fibers (GF) are chopped glass fibers, more preferably chopped glass fibers with a nominal diameter in the range from 5 to 30 μm, preferably in the range from 7 to 20 μm, most preferably in the range from 10 to 15 μm, and/or a chop length in the range from 1.0 to 10.0 mm, more preferably in the range from 2.0 to 7.0 mm, most preferably in the range from 3.0 to 5.0 mm.
The polyolefin composition (PC) according to any one of the preceding claims, further comprising:

e) from 0.1 to 2.5 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) , preferably a maleic anhydride-modified polypropylene.
The polyolefin composition (PC) according to claim 6, wherein the polar-modified polypropylene (PMP) has a content of polar groups in the range from 0.5 to 3.0 wt. -%.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the polyolefin composition (PC) has a flexural modulus, measured according to according to ISO 178 on 80x10x4 mm ³ test bars injection molded in line with EN ISO 1873-2, of at least 5000 MPa, and/or an Izod notched impact strength, measured according to EN ISO 180 using injection-molded bar test specimens of 80x10x4 mm ³ prepared in accordance with ISO 1873-2: 2007, of at least 5.0 kJ/m ².
The polyolefin composition (PC) according to any one of the preceding claims, wherein the polyolefin composition (PC) has a heat deflection temperature, measured according to ISO 75-2 under a load of 1.8 MPa, in the range from 140 to 160 ℃.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the polyolefin composition (PC) has a flame-retardancy classification, as measured according to test standard UL94-2013, of V-0.
An article comprising more than 75 wt. -%of the polyolefin composition (PC) according to any one of claims 1 to 10, preferably a molded article, most preferably an injection molded article.
The article according to claim 11, wherein the article is an automotive article, preferably the article is the housing for a storage battery in an electric vehicle.