Wannan labarin zai yi nazari kan manyan kayayyakin da ke cikin sarkar masana'antar C3 ta kasar Sin da kuma yadda ake gudanar da bincike da ci gaban fasahar zamani.

(1)Matsayin Halin Yanzu da Ci gaban Fasaha na Fasahar Polypropylene (PP).

Bisa ga bincikenmu, akwai hanyoyi daban-daban don samar da polypropylene (PP) a kasar Sin, daga cikinsu mafi mahimmancin matakai sun hada da tsarin bututun muhalli na gida, tsarin Unipol na Kamfanin Daoju, Tsarin Spheriol na Kamfanin LyondellBasell, Tsarin Innovene na Kamfanin Ineos, Novolen tsari. na Kamfanin Kemikal na Nordic, da tsarin Spherizone na Kamfanin LyondellBasell.Kamfanonin PP na kasar Sin sun karbe wadannan matakai.Waɗannan fasahohin galibi suna sarrafa adadin juzu'i na propylene a cikin kewayon 1.01-1.02.

Tsarin bututun zobe na cikin gida yana ɗaukar ƙirar ƙirar ZN mai zaman kanta, wanda fasahar sarrafa bututun zobe na ƙarni na biyu ke mamayewa a halin yanzu.Wannan tsari ya dogara ne akan abubuwan haɓakawa masu zaman kansu, fasaha mai ba da gudummawa ta lantarki, da fasahar propylene butadiene bazuwar fasahar copolymerization, kuma yana iya samar da homopolymerization, ethylene propylene bazuwar copolymerization, propylene butadiene bazuwar copolymerization, da tasiri resistant copolymerization PP.Misali, kamfanoni irin su Shanghai Petrochemical Line na Uku, da Refining na Zhenhai da Layin Sinadari na Farko da na Biyu, da Layin Maoming na Biyu duk sun yi amfani da wannan tsari.Tare da karuwar sabbin wuraren samar da kayayyaki a nan gaba, ana sa ran tsarin bututun muhalli na ƙarni na uku zai zama babban tsarin bututun muhalli na cikin gida a hankali.

Tsarin Unipol na iya samar da homopolymers a masana'antu, tare da ƙimar narkewa (MFR) kewayon 0.5 ~ 100g/10min.Bugu da kari, yawan juzu'i na ethylene copolymer monomers a cikin bazuwar copolymers na iya kaiwa 5.5%.Wannan tsari kuma zai iya samar da copolymer na masana'antu na propylene da 1-butene (sunan ciniki CE-FOR), tare da juzu'in juzu'i na roba har zuwa 14%.Yawan juzu'in ethylene a cikin tasirin copolymer da tsarin Unipol ke samarwa zai iya kaiwa 21% (yawan juzu'in roba shine 35%).An yi amfani da tsarin a cikin cibiyoyin kamfanoni kamar Fushun Petrochemical da Sichuan Petrochemical.

Tsarin Innovene zai iya samar da samfurori na homopolymer tare da nau'in nau'i mai yawa na narkewa (MFR), wanda zai iya kaiwa 0.5-100g / 10min.Ƙarfin samfurin sa ya fi na sauran tsarin polymerization na gas.MFR na samfuran copolymer bazuwar shine 2-35g/10min, tare da babban juzu'in ethylene daga 7% zuwa 8%.MFR na samfuran copolymer masu jure tasiri shine 1-35g/10min, tare da babban juzu'in ethylene daga 5% zuwa 17%.

A halin yanzu, fasahar samar da PP na yau da kullun a kasar Sin ta balaga sosai.Ɗaukar masana'antar polypropylene mai tushen a matsayin misali, babu wani gagarumin bambanci a cikin yawan amfani da naúrar, farashin sarrafawa, riba, da sauransu tsakanin kowace kamfani.Daga mahangar nau'ikan samarwa da matakai daban-daban suka rufe, manyan hanyoyin aiwatarwa na iya rufe dukkan nau'in samfurin.Koyaya, idan aka yi la'akari da ainihin nau'ikan fitarwa na masana'antar da ke akwai, akwai bambance-bambance masu yawa a cikin samfuran PP tsakanin masana'antu daban-daban saboda dalilai kamar yanayin ƙasa, shingen fasaha, da albarkatun ƙasa.

(2)Matsayin Yanzu da Ci gaban Fasahar Acrylic Acid

Acrylic acid wani muhimmin kayan sinadari ne da ake amfani da shi sosai wajen samar da kayan adhesives da mayuka masu narkewa da ruwa, sannan kuma ana sarrafa su zuwa butyl acrylate da sauran kayayyakin.Dangane da bincike, akwai matakai daban-daban na samarwa don acrylic acid, gami da hanyar chloroethanol, hanyar cyanoethanol, Hanyar Reppe mai ƙarfi, hanyar enone, ingantacciyar hanyar Reppe, hanyar formaldehyde ethanol, hanyar acrylonitrile hydrolysis, hanyar ethylene, hanyar propylene oxidation, da ilimin halitta. hanya.Ko da yake akwai dabarun shirye-shirye daban-daban don acrylic acid, kuma yawancin su an yi amfani da su a masana'antu, mafi yawan tsarin samar da kayan aiki a duk duniya har yanzu shine kai tsaye oxidation na propylene zuwa tsarin acrylic acid.

Abubuwan da ake amfani da su don samar da acrylic acid ta hanyar propylene oxidation sun hada da tururin ruwa, iska, da propylene.A lokacin aikin samarwa, waɗannan ukun suna fuskantar halayen iskar shaka ta hanyar gado mai ƙara kuzari a cikin wani yanki.Propylene ne da farko oxidized zuwa acrolein a cikin reactor na farko, sa'an nan kuma ƙara oxidized zuwa acrylic acid a na biyu reactor.Turin ruwa yana taka rawar dilution a cikin wannan tsari, yana guje wa faruwar fashe-fashe da kuma hana haɓakar halayen gefe.Duk da haka, baya ga samar da acrylic acid, wannan tsari na amsawa yana haifar da acetic acid da carbon oxides saboda halayen gefe.

A cewar binciken Pingtou Ge, mabuɗin fasahar aiwatar da iskar oxygen ta acrylic acid ya ta'allaka ne a cikin zaɓin abubuwan da ke haifar da kuzari.A halin yanzu, kamfanonin da za su iya samar da fasahar acrylic acid ta hanyar propylene oxidation sun hada da Sohio a Amurka, Japan Catalyst Chemical Company, Mitsubishi Chemical Company a Japan, BASF a Jamus, da Japan Chemical Technology.

Tsarin Sohio a cikin Amurka shine muhimmin tsari don samar da acrylic acid ta hanyar propylene oxidation, wanda ke nuna shi lokaci guda gabatar da propylene, iska, da tururin ruwa cikin jerin biyu da aka haɗa kafaffen gadon reactors, da kuma amfani da Mo Bi da Mo-V Multi-bangaren ƙarfe. oxides a matsayin mai kara kuzari, bi da bi.A karkashin wannan hanyar, yawan amfanin ƙasa na acrylic acid zai iya kaiwa kusan 80% (rabo na molar).Fa'idar hanyar Sohio ita ce, jerin reactors guda biyu na iya haɓaka rayuwar mai haɓakawa, har zuwa shekaru 2.Duk da haka, wannan hanya tana da lahani cewa ba za a iya dawo da propylene ba.

Hanyar BASF: Tun daga ƙarshen 1960s, BASF tana gudanar da bincike kan samar da acrylic acid ta hanyar propylene oxidation.Hanyar BASF tana amfani da Mo Bi ko Mo Co masu kara kuzari don amsawar iskar oxygen ta propylene, kuma yawan amfanin acrolein ta hanya ɗaya da aka samu zai iya kaiwa kusan 80% (rabin molar).Daga baya, ta amfani da Mo, W, V, da Fe masu haɓakawa, acrolein ya ƙara yin oxidized zuwa acrylic acid, tare da matsakaicin yawan amfanin gona na hanya ɗaya na kusan 90% (rabo na molar).Rayuwar haɓakar hanyar BASF na iya kaiwa shekaru 4 kuma tsarin yana da sauƙi.Duk da haka, wannan hanya tana da nakasawa kamar babban wurin tafasa mai ƙarfi, tsaftace kayan aiki akai-akai, da yawan amfani da makamashi gabaɗaya.

Hanyar mai kara kuzari na Jafananci: Hakanan ana amfani da na'urori masu kayyade kayyade biyu a jere da tsarin rabuwar hasumiya bakwai.Mataki na farko shi ne shigar da element Co cikin Mo Bi mai kara kuzari a matsayin mai kara kuzari, sannan a yi amfani da Mo, V, da Cu composite metal oxides a matsayin babban abin da ke kara kuzari a cikin reactor na biyu, wanda ke samun goyon bayan silica da gubar monoxide.A karkashin wannan tsari, yawan amfanin ƙasa na acrylic acid shine kusan 83-86% (rabo na molar).Hanyar samar da wutar lantarki ta Jafananci ta ɗauki madaidaicin madaurin gado guda ɗaya da tsarin rabuwa mai hasumiya 7, tare da ci gaba mai haɓakawa, yawan amfanin ƙasa gabaɗaya, da ƙarancin kuzari.Wannan hanyar a halin yanzu tana ɗaya daga cikin hanyoyin samar da ci gaba, daidai da tsarin Mitsubishi a Japan.

(3)Matsayin Yanzu da Ci gaban Fasahar Butyl Acrylate

Butyl acrylate wani ruwa ne mara launi wanda ba ya narkewa a cikin ruwa kuma ana iya haɗe shi da ethanol da ether.Ana buƙatar adana wannan fili a cikin ɗakin ajiya mai sanyi kuma mai iska.Acrylic acid da esters ana amfani dasu sosai a masana'antu.Ba wai kawai ana amfani da su don kera monomers masu laushi na acrylate mai ƙarfi da mannen ruwan shafa ba, amma kuma ana iya haɗa su da homopolymerized, copolymerized da graft copolymerized su zama polymer monomers kuma ana amfani da su azaman tsaka-tsakin haɗakar kwayoyin halitta.

A halin yanzu, tsarin samar da butyl acrylate ya ƙunshi amsawar acrylic acid da butanol a gaban toluene sulfonic acid don samar da butyl acrylate da ruwa.Halin esterification da ke cikin wannan tsari shine halayen juzu'i na yau da kullun, kuma wuraren tafasa na acrylic acid da samfurin butyl acrylate suna kusa.Saboda haka, yana da wuya a raba acrylic acid ta amfani da distillation, kuma acrylic acid ba za a iya sake yin amfani da shi ba.

Ana kiran wannan tsari butyl acrylate esterification method, galibi daga Cibiyar Nazarin Injiniya ta Jilin Petrochemical da sauran cibiyoyin da ke da alaƙa.Wannan fasaha ta riga ta girma sosai, kuma ikon sarrafa na'urar don acrylic acid da n-butanol daidai ne, yana iya sarrafa yawan amfani da naúrar tsakanin 0.6.Bugu da ƙari, wannan fasaha ta riga ta sami haɗin gwiwa da canja wuri.

(4)Matsayin Yanzu da Ci gaban Fasahar CPP

An yi fim ɗin CPP daga polypropylene a matsayin babban albarkatun ƙasa ta hanyar takamaiman hanyoyin sarrafawa irin su simintin simintin gyare-gyaren T-dimbin yawa.Wannan fim yana da kyakkyawan juriya na zafi kuma, saboda abubuwan da ke tattare da saurin sanyaya, zai iya samar da kyakkyawan santsi da nuna gaskiya.Sabili da haka, don aikace-aikacen marufi waɗanda ke buƙatar babban haske, fim ɗin CPP shine kayan da aka fi so.Mafi yawan amfani da fim din CPP shine a cikin kayan abinci na abinci, da kuma samar da kayan aikin aluminum, kayan aikin magunguna, da adana 'ya'yan itatuwa da kayan marmari.

A halin yanzu, tsarin samar da fina-finai na CPP shine babban simintin motsa jiki.Wannan tsari na samarwa ya ƙunshi masu fitar da kaya masu yawa, masu rarraba tashoshi da yawa (wanda aka fi sani da "feeders"), T-dimbin mutun mutun, tsarin simintin gyare-gyare, tsarin gogayya a kwance, oscillators, da tsarin iska.Babban halayen wannan tsari na samarwa shine kyawawa mai kyau, high flatness, ƙananan kauri haƙuri, kyakkyawan aikin haɓaka injiniyoyi, sassauci mai kyau, da kuma nuna gaskiya na samfuran fim na bakin ciki da aka samar.Yawancin masana'antun duniya na CPP suna amfani da hanyar simintin haɗin gwiwa don samarwa, kuma fasahar kayan aiki ta balaga.

Tun daga tsakiyar shekarun 1980, kasar Sin ta fara bullo da na'urorin shirya fina-finai na kasashen waje, amma galibin su gine-gine ne masu layi daya kuma suna cikin matakin farko.Bayan shiga cikin 1990s, kasar Sin ta gabatar da layukan samar da fina-finai na multi-layer co polymer cast daga kasashe irin su Jamus, Japan, Italiya, da Ostiriya.Wadannan kayan aiki da fasahohin da ake shigo da su daga kasashen waje su ne babban karfin masana'antar shirya fina-finai ta kasar Sin.Babban masu samar da kayan aiki sun haɗa da Bruckner na Jamus, Bartenfield, Leifenhauer, da Orchid na Austria.Tun daga shekarar 2000, kasar Sin ta bullo da sabbin layukan samar da kayayyaki na zamani, kuma kayayyakin da ake samarwa a cikin gida ma sun samu ci gaba cikin sauri.

Koyaya, idan aka kwatanta da matakin ci gaba na ƙasa da ƙasa, har yanzu akwai wani tazara a matakin sarrafa kansa, tsarin auna sarrafa extrusion, kaurin fim ɗin daidaita mutun kai tsaye, tsarin dawo da kayan kan layi, da iska ta atomatik na kayan aikin fim na gida.A halin yanzu, manyan masu samar da kayan aikin fasahar fim na CPP sun haɗa da Bruckner na Jamus, Leifenhauser, da Lanzin na Austria, da sauransu.Waɗannan masu ba da kayayyaki na ƙasashen waje suna da fa'idodi masu mahimmanci ta fuskar sarrafa kansa da sauran fannoni.Duk da haka, tsarin na yanzu ya riga ya balaga, kuma saurin haɓaka fasahar kayan aiki yana jinkirin, kuma babu wani kofa don haɗin gwiwa.

(5)Matsayin Yanzu da Ci gaban Fasaha na Fasahar Acrylonitrile

Propylene ammonia oxidation fasaha a halin yanzu shine babban hanyar samar da kasuwanci don acrylonitrile, kuma kusan dukkanin masana'antun acrylonitrile suna amfani da BP (SOHIO).Duk da haka, akwai kuma da yawa wasu masu samar da kuzari da za a zaɓa daga, irin su Mitsubishi Rayon (tsohon Nitto) da Asahi Kasei daga Japan, Hawan Ayyukan Ayyuka (tsohon Solutia) daga Amurka, da Sinopec.

Fiye da 95% na tsire-tsire na acrylonitrile a duk duniya suna amfani da fasahar propylene ammonia oxidation (wanda kuma aka sani da tsarin sohio) wanda BP ya yi majagaba kuma ya haɓaka.Wannan fasaha tana amfani da propylene, ammonia, iska, da ruwa a matsayin kayan danye, kuma tana shiga cikin reactor a wani kaso.A karkashin aikin phosphorus molybdenum bismuth ko antimony iron catalysts da aka goyan bayan silica gel, acrylonitrile yana haifar da zazzabi na 400-500.℃da kuma matsa lamba na yanayi.Sa'an nan, bayan jerin tsaka-tsaki, sha, hakar, dehydrocyanation, da matakan distillation, ana samun samfurin karshe na acrylonitrile.Hanyoyin da aka samu ta hanyar wannan hanya na iya kaiwa kashi 75%, kuma abubuwan da aka samo sun hada da acetonitrile, hydrogen cyanide, da ammonium sulfate.Wannan hanya tana da ƙimar samar da masana'antu mafi girma.

Tun daga 1984, Sinopec ta sanya hannu kan wata yarjejeniya ta dogon lokaci tare da INEOS kuma an ba ta izinin yin amfani da fasahar acrylonitrile na INEOS mai haƙƙin mallaka a China.Bayan shekaru na ci gaba, Cibiyar Nazarin Man Fetur ta Shanghai ta Sinopec ta sami nasarar samar da hanyar fasaha don samar da sinadarin propylene ammonia don samar da acrylonitrile, kuma ta gina kashi na biyu na aikin acrylonitrile na reshen Sinopec Anqing mai nauyin ton 130000.An yi nasarar aiwatar da aikin a cikin watan Janairun 2014, wanda ya kara karfin samar da sinadarin acrylonitrile a shekara daga tan 80000 zuwa tan 210000, ya zama muhimmin bangare na tushen samar da acrylonitrile na Sinopec.

A halin yanzu, kamfanoni a duk duniya tare da haƙƙin mallaka don fasahar propylene ammonia oxidation sun haɗa da BP, DuPont, Ineos, Asahi Chemical, da Sinopec.Wannan tsari na samar da balagagge kuma yana da saukin samu, kuma kasar Sin ma ta samu nasarar mayar da wannan fasaha ta gida, kuma aikinta bai yi kasa da fasahohin samar da kayayyaki na kasashen waje ba.

(6)Matsayin Yanzu da Ci gaban Fasaha na ABS

Bisa ga binciken, hanyar aiwatar da na'urar ABS an raba shi ne zuwa hanyar dasa ruwan shafa fuska da ci gaba da babbar hanyar.An haɓaka resin ABS bisa gyare-gyaren guduro polystyrene.A cikin 1947, kamfanin roba na Amurka ya karɓi tsarin haɗakarwa don cimma nasarar samar da resin ABS na masana'antu;A cikin 1954, Kamfanin BORG-WAMER a Amurka ya ƙera ruwan shafa fuska polymerized guduro ABS kuma ya sami samar da masana'antu.Bayyanar maganin shafawa ya inganta saurin ci gaban masana'antar ABS.Tun daga shekarun 1970s, fasahar samar da fasaha ta ABS ta shiga cikin babban ci gaba.

Hanyar daskarewa ruwan shafa wani tsari ne mai ci gaba, wanda ya haɗa da matakai guda huɗu: haɗin butadiene latex, haɗakar polymer graft, kira na styrene da acrylonitrile polymers, da haɗuwa bayan magani.Takamammen ƙayyadaddun tsari ya haɗa da naúrar PBL, ƙungiyar grafting, sashin SAN, da naúrar haɗawa.Wannan tsarin samarwa yana da babban matakin balaga na fasaha kuma an yi amfani da shi sosai a duk duniya.

A halin yanzu, babbar fasahar ABS ta fito ne daga kamfanoni irin su LG a Koriya ta Kudu, JSR a Japan, Dow a Amurka, New Lake Oil Chemical Co., Ltd. a Koriya ta Kudu, da Kellogg Technology a Amurka, dukkaninsu. wanda ke da babban matakin girma na fasaha na duniya.Tare da ci gaba da ci gaban fasaha, tsarin samar da ABS kuma yana ci gaba da ingantawa da ingantawa.A nan gaba, ingantattun hanyoyin samar da muhalli, da kyautata muhalli, da samar da makamashi na iya fitowa, wanda zai kawo karin damammaki da kalubale ga ci gaban masana'antar sinadarai.

(7)Matsayin fasaha da ci gaba na n-butanol

Dangane da abubuwan da aka lura, fasaha ta yau da kullun don haɗa butanol da octanol a duk duniya ita ce tsarin haɗakarwar carbonyl low-matsa lamba mai ruwa-lokaci cyclic.Babban albarkatun kasa don wannan tsari shine propylene da iskar gas.Daga cikin su, propylene galibi yana fitowa ne daga haɗaɗɗen samar da kai, tare da na'ura mai amfani da propylene tsakanin 0.6 da 0.62 ton.Ana yin iskar gas ɗin roba galibi daga iskar gas mai shayewa ko iskar gas mai tushen ci, tare da amfani da naúrar tsakanin mita 700 zuwa 720.

Fasahar hada-hadar carbonyl mai ƙarancin matsin lamba wanda Dow/David ya ɓullo da – tsarin zagayawa na ruwa-lokaci yana da fa'ida kamar babban canjin propylene, rayuwar sabis mai ƙarfi mai ƙarfi, da rage fitar da sharar gida uku.Wannan tsari a halin yanzu shi ne mafi ci gaba da fasaha na samarwa kuma ana amfani da shi sosai a cikin kamfanonin butanol da octanol na kasar Sin.

Ganin cewa fasahar Dow/David tana da ɗan girma kuma ana iya amfani da ita tare da haɗin gwiwar masana'antun cikin gida, kamfanoni da yawa za su ba da fifikon wannan fasaha yayin zabar saka hannun jari a ginin rukunin octanol na butanol, sannan fasahar cikin gida ta biyo baya.

(8)Matsayin Yanzu da Ci gaban Fasahar Polyacrylonitrile

Ana samun polyacrylonitrile (PAN) ta hanyar polymerization na kyauta na acrylonitrile kuma yana da mahimmanci a cikin shirye-shiryen filaye na acrylonitrile (acrylic fibers) da polyacrylonitrile na tushen carbon fibers.Yana bayyana a cikin farar fata ko ɗan ƙaramin rawaya siffan foda, tare da yanayin canjin gilashin kusan 90℃.Ana iya narkar da shi a cikin abubuwan kaushi na kwayoyin halitta irin su dimethylformamide (DMF) da dimethyl sulfoxide (DMSO), da kuma a cikin abubuwan da aka tattara na ruwa na salts inorganic kamar thiocyanate da perchlorate.Shirye-shiryen polyacrylonitrile galibi ya ƙunshi polymerization bayani ko hazo mai ruwa-ruwa na polymerization na acrylonitrile (AN) tare da monomers marasa ionic na biyu da ionic monomers na uku.

Ana amfani da polyacrylonitrile galibi don kera zaruruwan acrylic, waɗanda zaruruwan roba ne da aka yi daga acrylonitrile copolymers tare da yawan adadin sama da 85%.Dangane da kaushi da aka yi amfani da su a cikin tsarin samarwa, ana iya bambanta su azaman dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAc), sodium thiocyanate (NaSCN), da dimethyl formamide (DMF).Babban bambanci tsakanin sauran kaushi daban-daban shine solubility a cikin polyacrylonitrile, wanda ba shi da tasiri mai mahimmanci akan tsarin samar da polymerization na musamman.Bugu da kari, bisa ga daban-daban comonomers, ana iya raba su zuwa itaconic acid (IA), methyl acrylate (MA), acrylamide (AM), da methyl methacrylate (MMA), da dai sauransu. samfurin Properties na polymerization halayen.

Tsarin tarawa na iya zama mataki ɗaya ko mataki biyu.Hanyar mataki ɗaya tana nufin polymerization na acrylonitrile da comonomers a cikin yanayin bayani a lokaci ɗaya, kuma ana iya shirya samfuran kai tsaye cikin maganin kadi ba tare da rabuwa ba.Dokar mataki biyu tana nufin dakatar da polymerization na acrylonitrile da comonomers a cikin ruwa don samun polymer, wanda aka rabu, wanke, bushewa, da sauran matakai don samar da maganin kadi.A halin yanzu, tsarin samar da polyacrylonitrile na duniya yana da asali iri ɗaya, tare da bambanci a cikin hanyoyin polymerization na ƙasa da kuma co monomers.A halin yanzu, yawancin filaye na polyacrylonitrile a cikin ƙasashe daban-daban na duniya an yi su ne daga ternary copolymers, tare da acrylonitrile lissafin kashi 90% da ƙari na monomer na biyu daga 5% zuwa 8%.Manufar ƙara monomer na biyu shine don haɓaka ƙarfin injina, elasticity, da rubutu na zaruruwa, da haɓaka aikin rini.Hanyoyin da aka fi amfani da su sun hada da MMA, MA, vinyl acetate, da dai sauransu. Ƙarin adadin na monomer na uku shine 0.3% -2%, tare da manufar gabatar da wani adadin nau'in rini na hydrophilic don ƙara kusanci da zaruruwa tare da rini, waɗanda suke. Kasu kashi kashi cationic rini kungiyoyin da acidic rini kungiyoyin.

A halin yanzu, Japan ita ce babban wakilin tsarin duniya na polyacrylonitrile, sannan kasashe kamar Jamus da Amurka.Kamfanoni na wakilci sun hada da Zoltek, Hexcel, Cytec da Aldila daga Japan, Dongbang, Mitsubishi da Amurka, SGL daga Jamus da Formosa Plastics Group daga Taiwan, China, China.A halin yanzu, fasahar samar da kayan aiki na duniya na polyacrylonitrile ya balaga, kuma babu wuri mai yawa don inganta samfurin.